A field investigation into the impact of task demands on worker responses in the South African forestry silviculture sector
- Authors: Parker, Rhiannon Jennifer
- Date: 2014
- Subjects: Forests and forestry -- South Africa -- KwaZulu-Natal , Blue collar workers -- South Africa -- KwaZulu-Natal , Manual work -- South Africa -- KwaZulu-Natal , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5157 , http://hdl.handle.net/10962/d1015645
- Description: Background: In South Africa, limited research has focused on the task demands and workers responses associated with forestry silviculture work, particularly pitting and planting. The methods currently in use are manual, but despite our lack of understanding of the existing demands, advances in forestry engineering have resulted in an introduction of semi-mechanised versions of these tasks. This project aimed to compare the task demands of silviculture tasks using the current manual techniques and the more modern, semi-mechanised techniques. Methods: A holistic investigation focused on the worker characteristics of a sample of black male pitters and black female planters from the Kwa-Zulu Natal forestry industry, as well as biomechanical (spinal kinematics and L5/S1 forces), physiological (heart rate, oxygen consumption and energy expenditure) and psychophysical (ratings of perceived exertion and body discomfort) responses associated with manual and semi-mechanised pitting and planting. Results: The pitting task saw significant improvements in the spinal kinematic measures as a result of the increased mechanisation, with eight of the 16 recorded variables decreasing to a lower level of risk classification. Physiologically, the manual task was associated with a mean heart rate of 157 bt.min⁻¹ and absolute energy expenditure of 11.27 kcal.min⁻¹, which were not found to be significantly different to the values of 143 bt.min⁻¹ and 9.8 kcal.min⁻¹ recorded during the semi-mechanised technique. Psychophysical responses indicated that the workers perceived manual pitting to be more physically demanding than the semi-mechanised method. The manual and semi-mechanised planting tasks were, in general, found to be acceptable from a spinal kinematics perspective, with the majority of variables classified as low risk. However, the maximum sagittal angle was reduced by more than 20 degrees as a result of the new equipment. The physiological and psychophysical demands associated with manual planting were found to be within acceptable limits. Conclusion: In terms of pitting, it can tentatively be concluded that the semi-mechanised technique is better than the manual one, based on the biomechanical and psychophysical findings, however physiological demands require further investigation. When considering the planting techniques, the semi-mechanised method showed a slight improvement from the biomechanical perspective, but further physiological and psychophysical investigations are needed.
- Full Text:
- Authors: Parker, Rhiannon Jennifer
- Date: 2014
- Subjects: Forests and forestry -- South Africa -- KwaZulu-Natal , Blue collar workers -- South Africa -- KwaZulu-Natal , Manual work -- South Africa -- KwaZulu-Natal , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5157 , http://hdl.handle.net/10962/d1015645
- Description: Background: In South Africa, limited research has focused on the task demands and workers responses associated with forestry silviculture work, particularly pitting and planting. The methods currently in use are manual, but despite our lack of understanding of the existing demands, advances in forestry engineering have resulted in an introduction of semi-mechanised versions of these tasks. This project aimed to compare the task demands of silviculture tasks using the current manual techniques and the more modern, semi-mechanised techniques. Methods: A holistic investigation focused on the worker characteristics of a sample of black male pitters and black female planters from the Kwa-Zulu Natal forestry industry, as well as biomechanical (spinal kinematics and L5/S1 forces), physiological (heart rate, oxygen consumption and energy expenditure) and psychophysical (ratings of perceived exertion and body discomfort) responses associated with manual and semi-mechanised pitting and planting. Results: The pitting task saw significant improvements in the spinal kinematic measures as a result of the increased mechanisation, with eight of the 16 recorded variables decreasing to a lower level of risk classification. Physiologically, the manual task was associated with a mean heart rate of 157 bt.min⁻¹ and absolute energy expenditure of 11.27 kcal.min⁻¹, which were not found to be significantly different to the values of 143 bt.min⁻¹ and 9.8 kcal.min⁻¹ recorded during the semi-mechanised technique. Psychophysical responses indicated that the workers perceived manual pitting to be more physically demanding than the semi-mechanised method. The manual and semi-mechanised planting tasks were, in general, found to be acceptable from a spinal kinematics perspective, with the majority of variables classified as low risk. However, the maximum sagittal angle was reduced by more than 20 degrees as a result of the new equipment. The physiological and psychophysical demands associated with manual planting were found to be within acceptable limits. Conclusion: In terms of pitting, it can tentatively be concluded that the semi-mechanised technique is better than the manual one, based on the biomechanical and psychophysical findings, however physiological demands require further investigation. When considering the planting techniques, the semi-mechanised method showed a slight improvement from the biomechanical perspective, but further physiological and psychophysical investigations are needed.
- Full Text:
Cardiovascular disease risk in Black African females and the efficacy of a walking programme on blood pressure in a sub-sample
- Authors: Crymble, Tegan
- Date: 2014
- Subjects: Cardiovascular system -- Diseases -- South Africa -- Eastern Cape , Women -- Health and hygiene -- South Africa -- Eastern Cape , Obesity -- South Africa -- Eastern Cape , Hypertension -- South Africa -- Eastern Cape , Walking -- South Africa -- Eastern Cape -- Physiological aspects , Lifestyles -- Health aspects -- South Africa -- Eastern Cape , Health attitudes -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5152 , http://hdl.handle.net/10962/d1013234
- Description: The purpose of the study was to investigate the cardiovascular disease (CVD) risk profile of black African females in the Makana region, Eastern Cape, South Africa. Baseline measures from 40 participants, who met the criteria, were compared against the 2003 South African Demographic and Health Survey (SADHS) and the 2013 South African National Health and Nutritional Examination Survey (SANHANES-1). The risk factors measured were anthropometric (stature, body mass and body mass index (BMI)), morphological (waist circumference (WC), fat mass and lean mass), cardiovascular (heart rate and blood pressure (BP)), physical activity (step count and energy expenditure), biochemical (glycated haemoglobin and full blood lipid profile) and behavioural (alcohol and tobacco use). Results showed significantly higher (p≤0.05) values for overweight/obesity (BMI 37.60 kg.m⁻²; WC 1130.58 mm; fat mass 45.23%) and high BP (130/88 mmHg) compared to the previous national surveys, highlighting these CVD risk factors as problematic. The subsequent sub-study aimed to assess the efficacy of a pedometer-based walking intervention on high BP. The walking programme (n=25) was based on individual step goals to be completed at a moderate-intensity on five days.week⁻¹ for 12 weeks. The same measurements were taken at monthly intervals, Week 0, Week 4, Week 8 and Week 12, with the addition of dietary intake and fitness level, and the exclusion of the behavioural variables. There were no significant differences (p≤0.05) in systolic and diastolic BP with the exercise intervention, although there was a strong, negative relationship with time for diastolic BP (r²=0.9857). This trend suggests that the lack of significance may be a result of poor compliance and/or the small sample size. Individual results, however, showed no compliance-result relationship for the two risk factors of interest: overweight/obesity and high BP. Future recommendations include supervised or group-based exercise interventions to improve compliance, and the addition of resistance training to the aerobic programme.
- Full Text:
- Authors: Crymble, Tegan
- Date: 2014
- Subjects: Cardiovascular system -- Diseases -- South Africa -- Eastern Cape , Women -- Health and hygiene -- South Africa -- Eastern Cape , Obesity -- South Africa -- Eastern Cape , Hypertension -- South Africa -- Eastern Cape , Walking -- South Africa -- Eastern Cape -- Physiological aspects , Lifestyles -- Health aspects -- South Africa -- Eastern Cape , Health attitudes -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5152 , http://hdl.handle.net/10962/d1013234
- Description: The purpose of the study was to investigate the cardiovascular disease (CVD) risk profile of black African females in the Makana region, Eastern Cape, South Africa. Baseline measures from 40 participants, who met the criteria, were compared against the 2003 South African Demographic and Health Survey (SADHS) and the 2013 South African National Health and Nutritional Examination Survey (SANHANES-1). The risk factors measured were anthropometric (stature, body mass and body mass index (BMI)), morphological (waist circumference (WC), fat mass and lean mass), cardiovascular (heart rate and blood pressure (BP)), physical activity (step count and energy expenditure), biochemical (glycated haemoglobin and full blood lipid profile) and behavioural (alcohol and tobacco use). Results showed significantly higher (p≤0.05) values for overweight/obesity (BMI 37.60 kg.m⁻²; WC 1130.58 mm; fat mass 45.23%) and high BP (130/88 mmHg) compared to the previous national surveys, highlighting these CVD risk factors as problematic. The subsequent sub-study aimed to assess the efficacy of a pedometer-based walking intervention on high BP. The walking programme (n=25) was based on individual step goals to be completed at a moderate-intensity on five days.week⁻¹ for 12 weeks. The same measurements were taken at monthly intervals, Week 0, Week 4, Week 8 and Week 12, with the addition of dietary intake and fitness level, and the exclusion of the behavioural variables. There were no significant differences (p≤0.05) in systolic and diastolic BP with the exercise intervention, although there was a strong, negative relationship with time for diastolic BP (r²=0.9857). This trend suggests that the lack of significance may be a result of poor compliance and/or the small sample size. Individual results, however, showed no compliance-result relationship for the two risk factors of interest: overweight/obesity and high BP. Future recommendations include supervised or group-based exercise interventions to improve compliance, and the addition of resistance training to the aerobic programme.
- Full Text:
Impact of batting skill on pacing during repeated sprints between the wickets.
- Authors: Elliott, Andrea
- Date: 2014
- Subjects: Cricket -- Batting -- Research , Sprinting -- Research , Cricket players , Exercise -- Physiological aspects -- Research , Sports -- Physiological aspects -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5153 , http://hdl.handle.net/10962/d1013546
- Description: Introduction: With batting in cricket, there is no known end point, making the allocation of resources and the development of a suitable pacing strategy more difficult. How batsmen allocate resources and pace themselves when repeatedly sprinting between the wickets is therefore not known. According to the ‘anticipatory feedback’ model, the level of expertise/experience has a substantial influence on the development of a suitable pacing strategy. Skilled or experienced batsmen may therefore have a greater ability to develop and implement a pacing strategy compared to that of novice or less-skilled batsmen. Purpose: To assess whether the absence of a known end point at the beginning of repeated sprint bouts between the wickets effects how batsmen pace themselves comparing skilled and less-skilled batsmen. Methods: Twenty-four male cricketers from a university league were selected. Twelve skilled batsmen (players in the top five batting order), and 12 less-skilled batsmen (players in the bottom five batting order) completed three experimental. All trials required batsmen to complete the same number of shuttle sprints (14 shuttles and therefore 28 runs), while only the information provided before each trial differed. Control Trial: This trial is also referred to as the ‘informed’ trial as the batsmen are aware of the exercise requirements (end point). Unknown Trial: The batsmen were not informed of the exercise end point and were required to run on command for an indefinite period (28 runs). Deceptive Trial: Batsmen’ were incorrectly informed with regards to the number of sprints (told they were only doing 14 runs when in fact they were doing 28 runs). Muscle activity, sprint times and RPE measures were obtained during all three trials and compared. Results: Significant (p<0.05) group effects were apparent for sprint times and, ‘central’ and ‘local’ RPE. Specifically, skilled batsmen obtained the faster mean sprint times, and less-skilled batsmen reported the higher mean ‘central’ and ‘local’ RPE values in all three experimental trials. There were no significant group effects for muscle activation. Skilled batsmen did however have lower muscle activation compared to less-skilled batsmen in all three trials. Furthermore, general trends revealed that sprint times and muscle activation decreased over time (from shuttle 1 to shuttle 14), and RPE (‘central’ and ‘local’) ratings increased, regardless of the experimental trials. Skilled batsmen performed the best in all three trials. This was determined by the attainment of faster sprint times, lower muscle activation and low RPE ratings in each of the three trials. The assessment of the relationship of the dependent variables measured in each trial, did however suggest that skilled batsmen performed best in the deceptive trial while less-skilled batsmen performed best in the control trial. Skilled batsmen thus showed superior performance when trial requirements were unclear. Less-skilled batsmen however, were seen to experience decrements in performance when information regarding the end point was unknown or misleading. Conclusion: It can thus be concluded that previous experience facilitates in the obtainment of improved sprint times between the wickets, especially when the exact end point is unknown.
- Full Text:
- Authors: Elliott, Andrea
- Date: 2014
- Subjects: Cricket -- Batting -- Research , Sprinting -- Research , Cricket players , Exercise -- Physiological aspects -- Research , Sports -- Physiological aspects -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5153 , http://hdl.handle.net/10962/d1013546
- Description: Introduction: With batting in cricket, there is no known end point, making the allocation of resources and the development of a suitable pacing strategy more difficult. How batsmen allocate resources and pace themselves when repeatedly sprinting between the wickets is therefore not known. According to the ‘anticipatory feedback’ model, the level of expertise/experience has a substantial influence on the development of a suitable pacing strategy. Skilled or experienced batsmen may therefore have a greater ability to develop and implement a pacing strategy compared to that of novice or less-skilled batsmen. Purpose: To assess whether the absence of a known end point at the beginning of repeated sprint bouts between the wickets effects how batsmen pace themselves comparing skilled and less-skilled batsmen. Methods: Twenty-four male cricketers from a university league were selected. Twelve skilled batsmen (players in the top five batting order), and 12 less-skilled batsmen (players in the bottom five batting order) completed three experimental. All trials required batsmen to complete the same number of shuttle sprints (14 shuttles and therefore 28 runs), while only the information provided before each trial differed. Control Trial: This trial is also referred to as the ‘informed’ trial as the batsmen are aware of the exercise requirements (end point). Unknown Trial: The batsmen were not informed of the exercise end point and were required to run on command for an indefinite period (28 runs). Deceptive Trial: Batsmen’ were incorrectly informed with regards to the number of sprints (told they were only doing 14 runs when in fact they were doing 28 runs). Muscle activity, sprint times and RPE measures were obtained during all three trials and compared. Results: Significant (p<0.05) group effects were apparent for sprint times and, ‘central’ and ‘local’ RPE. Specifically, skilled batsmen obtained the faster mean sprint times, and less-skilled batsmen reported the higher mean ‘central’ and ‘local’ RPE values in all three experimental trials. There were no significant group effects for muscle activation. Skilled batsmen did however have lower muscle activation compared to less-skilled batsmen in all three trials. Furthermore, general trends revealed that sprint times and muscle activation decreased over time (from shuttle 1 to shuttle 14), and RPE (‘central’ and ‘local’) ratings increased, regardless of the experimental trials. Skilled batsmen performed the best in all three trials. This was determined by the attainment of faster sprint times, lower muscle activation and low RPE ratings in each of the three trials. The assessment of the relationship of the dependent variables measured in each trial, did however suggest that skilled batsmen performed best in the deceptive trial while less-skilled batsmen performed best in the control trial. Skilled batsmen thus showed superior performance when trial requirements were unclear. Less-skilled batsmen however, were seen to experience decrements in performance when information regarding the end point was unknown or misleading. Conclusion: It can thus be concluded that previous experience facilitates in the obtainment of improved sprint times between the wickets, especially when the exact end point is unknown.
- Full Text:
Strength training and cardiovascular risk post-menses, with particular emphasis on the plasma lipoproteins: a controlled trial
- Authors: Viljoen, Janet Erica
- Date: 2014
- Subjects: Weight training for women -- Physiological aspects , Exercise for women -- Physiological aspects , Middle-aged women -- Health and hygiene , Cardiovascular system -- Diseases , Hypercholesteremia , Blood lipoproteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5155 , http://hdl.handle.net/10962/d1013578
- Description: Introduction: Cardiovascular disease affects a greater proportion of females than it does males, and is responsible for an estimated 52 percent of female deaths per annum, globally. Due to the loss of oestrogen associated with the menopause, post-menopausal females are at elevated risk for hypercholesterolaemia which is a primary risk factor for cardiovascular disease. It has not yet been conclusively established whether resistance training can be used to ameliorate hypercholesterolaemia. Aim: This randomized controlled trial investigated what effect 12 weeks of progressive resistance training would have on plasma lipoproteins in a sample of post-menopausal females. Methods: Caucasian women (n=30 intervention and n=18 control) between the ages of 55 and 65 years who were not taking hormone replacement therapy were recruited. Participants did not smoke, were sedentary, were not taking any form of cholesterol-lowering medication, had at least one cholesterol abnormality at baseline but were otherwise healthy and able to participate in a strength training programme. Following extensive medical pre-screening, information dissemination and voluntary consent, the sample was divided into two groups. The exercise sample undertook 12 weeks of resistance training on five days of the week. The control group received no intervention. Measurements were obtained at baseline and every four weeks thereafter and included measures of strength, biochemistry (oestradiol, testosterone, full blood lipid profile, glycated haemoglobin and sex hormone binding globulin), anthropometry, morphology and self-reports (dietary intake, energy expenditure and the profile of mood states questionnaire). Results: There was no change to low density lipoprotein cholesterol, high density lipoprotein cholesterol, triglyceride content or total cholesterol as a result of the intervention. Back, chest and leg strength increased significantly (p<0.01) (increases of 51 percent, 35 percent and 43 percent respectively from baseline); waist circumference dropped (p<0.01) by 5 percent overall and diastolic blood pressure decreased significantly (-9 percent, p<0.01) in the exercise cohort but no change was noted in the matched control. Dietary intake, energy expenditure and body mass remained unchanged in both samples. Morphology (sum of skinfolds, estimated body fat content and girth measures) did not change and nor did other biochemical measures (HbA1c and sex hormone binding globulin) or hormone levels (oestradiol and testosterone). Despite the lack of overall change, an important finding was noted in individual results where a clear indication of ‘responders’ and ‘non-responders’ emerged. Conclusion: Overall mean results suggest that 12 weeks resistance training undertaken five days of the week was ineffective in reducing hypercholesterolaemia in this sample. Despite there being no identifying characteristics determined in this sample, evidence of responders and non-responders to the intervention indicates that reliance on mean data may not be sufficient when analysing data from exercise interventions. Therefore, while progressive resistance training had a positive effect on strength, waist circumference and diastolic blood pressure, it did not positively influence the plasma lipoproteins in this cohort of post-menopausal women. , Maiden name: Kelly, Janet Erica
- Full Text:
- Authors: Viljoen, Janet Erica
- Date: 2014
- Subjects: Weight training for women -- Physiological aspects , Exercise for women -- Physiological aspects , Middle-aged women -- Health and hygiene , Cardiovascular system -- Diseases , Hypercholesteremia , Blood lipoproteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5155 , http://hdl.handle.net/10962/d1013578
- Description: Introduction: Cardiovascular disease affects a greater proportion of females than it does males, and is responsible for an estimated 52 percent of female deaths per annum, globally. Due to the loss of oestrogen associated with the menopause, post-menopausal females are at elevated risk for hypercholesterolaemia which is a primary risk factor for cardiovascular disease. It has not yet been conclusively established whether resistance training can be used to ameliorate hypercholesterolaemia. Aim: This randomized controlled trial investigated what effect 12 weeks of progressive resistance training would have on plasma lipoproteins in a sample of post-menopausal females. Methods: Caucasian women (n=30 intervention and n=18 control) between the ages of 55 and 65 years who were not taking hormone replacement therapy were recruited. Participants did not smoke, were sedentary, were not taking any form of cholesterol-lowering medication, had at least one cholesterol abnormality at baseline but were otherwise healthy and able to participate in a strength training programme. Following extensive medical pre-screening, information dissemination and voluntary consent, the sample was divided into two groups. The exercise sample undertook 12 weeks of resistance training on five days of the week. The control group received no intervention. Measurements were obtained at baseline and every four weeks thereafter and included measures of strength, biochemistry (oestradiol, testosterone, full blood lipid profile, glycated haemoglobin and sex hormone binding globulin), anthropometry, morphology and self-reports (dietary intake, energy expenditure and the profile of mood states questionnaire). Results: There was no change to low density lipoprotein cholesterol, high density lipoprotein cholesterol, triglyceride content or total cholesterol as a result of the intervention. Back, chest and leg strength increased significantly (p<0.01) (increases of 51 percent, 35 percent and 43 percent respectively from baseline); waist circumference dropped (p<0.01) by 5 percent overall and diastolic blood pressure decreased significantly (-9 percent, p<0.01) in the exercise cohort but no change was noted in the matched control. Dietary intake, energy expenditure and body mass remained unchanged in both samples. Morphology (sum of skinfolds, estimated body fat content and girth measures) did not change and nor did other biochemical measures (HbA1c and sex hormone binding globulin) or hormone levels (oestradiol and testosterone). Despite the lack of overall change, an important finding was noted in individual results where a clear indication of ‘responders’ and ‘non-responders’ emerged. Conclusion: Overall mean results suggest that 12 weeks resistance training undertaken five days of the week was ineffective in reducing hypercholesterolaemia in this sample. Despite there being no identifying characteristics determined in this sample, evidence of responders and non-responders to the intervention indicates that reliance on mean data may not be sufficient when analysing data from exercise interventions. Therefore, while progressive resistance training had a positive effect on strength, waist circumference and diastolic blood pressure, it did not positively influence the plasma lipoproteins in this cohort of post-menopausal women. , Maiden name: Kelly, Janet Erica
- Full Text:
The effects of age on the worker capacity and mechanisation on the task demands in a South African manufacturing industry
- Bezuidenhout, Samantha Catherine
- Authors: Bezuidenhout, Samantha Catherine
- Date: 2014
- Subjects: Age and employment -- South Africa , Labor -- Social aspects -- South Africa , Brickmaking -- South Africa -- Automation , Brickmaking -- Social aspects -- South Africa , Brick trade -- South Africa , Aging -- Social aspects -- South Africa , Aging -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5151 , http://hdl.handle.net/10962/d1013167
- Description: The focus of the study was two-fold, firstly to determine the effect of age on the capacity of manual materials handling workers and secondly to determine the effect of increasing task mechanisation on the workers’ responses to task demands. The first component of this study, namely Part I, 101 male and 12 female ‘unskilled’ manual workers – of various ages – from a brick manufacturing industry were assessed. Anthropometric, health and strength factors were measured to improve the understanding of the South African manual worker capacity and more specifically, the effect of age on this capacity. Data collection was done between 7.30am and 9.30am in a laboratory-type setting on-site. Anthropometric characteristics (including body mass index, waist to hip ratio, waist circumference and body fat percentage) provided information on the state of obesity and the impact of age in the South African context. Linked to this, the health factors (including blood pressure, resting heart rate and a self-reported questionnaire) provide an extra snapshot of the disease profile in South Africa, and could potentially influence other capacity factors. Isometric strength capacities (of eight different areas, namely: back, leg, bicep, shoulder, pinch, pinch and pull) demonstrated whether South African manual workers show the same decline in strength with aging as seen in industrially advanced countries. The second component of the study, Part II, was performed in situ and measured the workers’ responses to task demands of three brick palletising tasks, one manual (n=21) and two with increasing mechanisation (n=12 each). Spinal kinematics, joint forces and working heart rate were assessed on normal work days during a 30-lift duration and body discomfort measures were taken at the start, middle and end of the work-shift. Spinal kinematics were measured dynamically using a lumbar motion monitor, whereas the spinal forces were estimated using the three dimensional static strength prediction program. The worker capacity results showed that waist to hip ratio, waist circumference and body fat percentage increased significantly with aging, whereas body mass index was not affected by age. All body morphology values were within ‘normal’ ranges. Although diastolic blood pressure increased significantly with age, systolic was not affected significantly by age. Both groups, however, showed an increasing prevalence of hypertension with aging. There were no significant changes in resting heart rate with aging, with a range of 66 bt.min⁻¹ to 74.86 bt.min⁻¹, therefore within normal ranges. Of the strength factors, age only affected shoulder and push strength significantly: Showing a decrease in shoulder strength from 49.89 kgF to 39.91 kgF in the men aged 20-29 to the 50-59 respectively and an increase in push strength from men aged 30-39 and 40-49 to those aged 50-59. Part II results revealed highly frequent lift rates and large degrees of sagittal flexion and lateral bending in all three tasks. These postures adopted for long durations are likely to lead to the development of musculoskeletal disorders. Heart rates of workers from the three tasks were significantly different and heart rates for two tasks were above the recommended 110 bt.min⁻¹. Similarly the body discomfort ratings of the three tasks differed, although a common trend was seen in that lower back pain was the most commonly reported area of discomfort in all tasks. South African manual materials handling males did not show the same responses to aging as men from industrially advanced countries, calling for further research into these differences. Due to the high risks of the three tasks assessed, future research and interventions are required to reduce the risk of injury in the assessed tasks.
- Full Text:
- Authors: Bezuidenhout, Samantha Catherine
- Date: 2014
- Subjects: Age and employment -- South Africa , Labor -- Social aspects -- South Africa , Brickmaking -- South Africa -- Automation , Brickmaking -- Social aspects -- South Africa , Brick trade -- South Africa , Aging -- Social aspects -- South Africa , Aging -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5151 , http://hdl.handle.net/10962/d1013167
- Description: The focus of the study was two-fold, firstly to determine the effect of age on the capacity of manual materials handling workers and secondly to determine the effect of increasing task mechanisation on the workers’ responses to task demands. The first component of this study, namely Part I, 101 male and 12 female ‘unskilled’ manual workers – of various ages – from a brick manufacturing industry were assessed. Anthropometric, health and strength factors were measured to improve the understanding of the South African manual worker capacity and more specifically, the effect of age on this capacity. Data collection was done between 7.30am and 9.30am in a laboratory-type setting on-site. Anthropometric characteristics (including body mass index, waist to hip ratio, waist circumference and body fat percentage) provided information on the state of obesity and the impact of age in the South African context. Linked to this, the health factors (including blood pressure, resting heart rate and a self-reported questionnaire) provide an extra snapshot of the disease profile in South Africa, and could potentially influence other capacity factors. Isometric strength capacities (of eight different areas, namely: back, leg, bicep, shoulder, pinch, pinch and pull) demonstrated whether South African manual workers show the same decline in strength with aging as seen in industrially advanced countries. The second component of the study, Part II, was performed in situ and measured the workers’ responses to task demands of three brick palletising tasks, one manual (n=21) and two with increasing mechanisation (n=12 each). Spinal kinematics, joint forces and working heart rate were assessed on normal work days during a 30-lift duration and body discomfort measures were taken at the start, middle and end of the work-shift. Spinal kinematics were measured dynamically using a lumbar motion monitor, whereas the spinal forces were estimated using the three dimensional static strength prediction program. The worker capacity results showed that waist to hip ratio, waist circumference and body fat percentage increased significantly with aging, whereas body mass index was not affected by age. All body morphology values were within ‘normal’ ranges. Although diastolic blood pressure increased significantly with age, systolic was not affected significantly by age. Both groups, however, showed an increasing prevalence of hypertension with aging. There were no significant changes in resting heart rate with aging, with a range of 66 bt.min⁻¹ to 74.86 bt.min⁻¹, therefore within normal ranges. Of the strength factors, age only affected shoulder and push strength significantly: Showing a decrease in shoulder strength from 49.89 kgF to 39.91 kgF in the men aged 20-29 to the 50-59 respectively and an increase in push strength from men aged 30-39 and 40-49 to those aged 50-59. Part II results revealed highly frequent lift rates and large degrees of sagittal flexion and lateral bending in all three tasks. These postures adopted for long durations are likely to lead to the development of musculoskeletal disorders. Heart rates of workers from the three tasks were significantly different and heart rates for two tasks were above the recommended 110 bt.min⁻¹. Similarly the body discomfort ratings of the three tasks differed, although a common trend was seen in that lower back pain was the most commonly reported area of discomfort in all tasks. South African manual materials handling males did not show the same responses to aging as men from industrially advanced countries, calling for further research into these differences. Due to the high risks of the three tasks assessed, future research and interventions are required to reduce the risk of injury in the assessed tasks.
- Full Text:
Validation of an assessment tool for mental fatigue applied to rotational shift work
- Authors: Huysamen, Kirsten Christina
- Date: 2014
- Subjects: Mental fatigue , Shift systems , Performance , Motor ability , Memory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5154 , http://hdl.handle.net/10962/d1013551
- Description: Mental fatigue has been proven to be highly prominent during shift work, due to long, irregular working hours and disruption of the circadian rhythm. Measuring mental fatigue has been a challenge for many years, where commonly cognitive test tasks are used to assess mental fatigue. Moreover, these test tasks do not isolate where fatigue is occurring during human information processing. The human information processing system consists of four core stages, each of which requires numerous cognitive functions in order to process information. The Human Kinetics and Ergonomics Department at Rhodes University has developed six cognitive test tasks where each isolates a cognitive function: an accommodation test task, a visual detection test task, a reading test task, a memory test task, a tapping test task and a neural control test task. The cognitive functions include: eye accommodation, visual discrimination, visual pattern recognition, memory duration, motor programming and peripheral neural control. General task-related effect can also be examined for each of these cognitive test tasks which include choice reaction time, visual detection, reading performance, short-term memory, motor control and tracking performance. Additionally, a simple reaction time test task has been developed to analyse simple reaction time. This test task does not isolate a cognitive function. One or more parameters can be examined for each cognitive function and task-related effect. The first aim of this study was to validate numerous cognitive test tasks for mental fatigue in a simulated shift work laboratory setting. The second aim was to assess the validated cognitive test tasks in Phase 1 in a field-based rotational shift work setting. Parameters revealing sensitivity to mental fatigue would be validated for mental fatigue applied to rotational shift work and would be inserted into an assessment tool. In the laboratory setting, the seven cognitive test tasks were examined on four different types of shift work regimes. The first regime was a standard eight-hour shift work system, and the other three were non-conventional shift work regimes. Participants (n = 12 per regime) were required to complete one day shift followed by four night shifts, where testing occurred before and after each shift and four times within each shift. The cognitive test tasks revealing sensitivity to fatigue included: visual detection test task, reading test task, memory test task, tapping test task, neural control test task and simple reaction time test task. The testing of Phase 2 was conducted in three different companies, where each performed a different type of rotational shift work. The six cognitive test tasks validated for mental fatigue in Phase 1 were tested before and after work for each shift type within the rotational shift work system adopted by each company. Company A (n = 18) and Company B (n = 24) performed two-shift rotational shift work systems, where the shift length of Company A was 12-hours and the shift length of Company B was irregular hours. Company C (n = 21) performed an eight-hour three-shift rotational shift work system. Nine parameters revealed fatiguing effects and were inserted into the assessment tool, five of which provided information on a specific cognitive function: error rate for visual discrimination, processing time for visual pattern recognition, error rate for visual pattern recognition, impact of rehearsal time on memory recall rate for memory duration and the high-precision condition for motor programming time. The remaining four parameters provided information on general task-related effects: reading speed for reading performance, recall rate for short-term memory, reaction time for motor control and simple reaction time. Therefore, an assessment tool comprising nine parameters was validated for mental fatigue applied to rotational shift work, where five of the parameters were able to isolate exactly where fatigue was occurring during human information processing and the other four parameters were able to assess fatigue occurring throughout the human information processing chain.
- Full Text:
- Authors: Huysamen, Kirsten Christina
- Date: 2014
- Subjects: Mental fatigue , Shift systems , Performance , Motor ability , Memory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5154 , http://hdl.handle.net/10962/d1013551
- Description: Mental fatigue has been proven to be highly prominent during shift work, due to long, irregular working hours and disruption of the circadian rhythm. Measuring mental fatigue has been a challenge for many years, where commonly cognitive test tasks are used to assess mental fatigue. Moreover, these test tasks do not isolate where fatigue is occurring during human information processing. The human information processing system consists of four core stages, each of which requires numerous cognitive functions in order to process information. The Human Kinetics and Ergonomics Department at Rhodes University has developed six cognitive test tasks where each isolates a cognitive function: an accommodation test task, a visual detection test task, a reading test task, a memory test task, a tapping test task and a neural control test task. The cognitive functions include: eye accommodation, visual discrimination, visual pattern recognition, memory duration, motor programming and peripheral neural control. General task-related effect can also be examined for each of these cognitive test tasks which include choice reaction time, visual detection, reading performance, short-term memory, motor control and tracking performance. Additionally, a simple reaction time test task has been developed to analyse simple reaction time. This test task does not isolate a cognitive function. One or more parameters can be examined for each cognitive function and task-related effect. The first aim of this study was to validate numerous cognitive test tasks for mental fatigue in a simulated shift work laboratory setting. The second aim was to assess the validated cognitive test tasks in Phase 1 in a field-based rotational shift work setting. Parameters revealing sensitivity to mental fatigue would be validated for mental fatigue applied to rotational shift work and would be inserted into an assessment tool. In the laboratory setting, the seven cognitive test tasks were examined on four different types of shift work regimes. The first regime was a standard eight-hour shift work system, and the other three were non-conventional shift work regimes. Participants (n = 12 per regime) were required to complete one day shift followed by four night shifts, where testing occurred before and after each shift and four times within each shift. The cognitive test tasks revealing sensitivity to fatigue included: visual detection test task, reading test task, memory test task, tapping test task, neural control test task and simple reaction time test task. The testing of Phase 2 was conducted in three different companies, where each performed a different type of rotational shift work. The six cognitive test tasks validated for mental fatigue in Phase 1 were tested before and after work for each shift type within the rotational shift work system adopted by each company. Company A (n = 18) and Company B (n = 24) performed two-shift rotational shift work systems, where the shift length of Company A was 12-hours and the shift length of Company B was irregular hours. Company C (n = 21) performed an eight-hour three-shift rotational shift work system. Nine parameters revealed fatiguing effects and were inserted into the assessment tool, five of which provided information on a specific cognitive function: error rate for visual discrimination, processing time for visual pattern recognition, error rate for visual pattern recognition, impact of rehearsal time on memory recall rate for memory duration and the high-precision condition for motor programming time. The remaining four parameters provided information on general task-related effects: reading speed for reading performance, recall rate for short-term memory, reaction time for motor control and simple reaction time. Therefore, an assessment tool comprising nine parameters was validated for mental fatigue applied to rotational shift work, where five of the parameters were able to isolate exactly where fatigue was occurring during human information processing and the other four parameters were able to assess fatigue occurring throughout the human information processing chain.
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An analysis of regulatory mechanisms during sustained task execution in cognitive, motor and sensory tasks
- Tau, Sethunya Harriet Hlobisa
- Authors: Tau, Sethunya Harriet Hlobisa
- Date: 2013 , 2013-10-11
- Subjects: Work -- Physiological aspects , Work -- Psychological aspects , Fatigue , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Employees -- Workload , Performance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5140 , http://hdl.handle.net/10962/d1006806 , Work -- Physiological aspects , Work -- Psychological aspects , Fatigue , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Employees -- Workload , Performance
- Description: Fatigue is a state that, although researched for many years, is still not completely understood. Alongside this lack of a general understanding of fatigue is a lack of knowledge on the processes involved in the regulation of fatigue. The existing theories relating to regulation are focussed on mental effort regulation, suggesting that performance outcomes are co-ordinated by effort regulation that functions by making alterations to physiological processes and strategic adjustments at a cognitive level in response to cognitive demands and goals. Since fatigue is a multi-dimensional construct with psychological, physiological, and behavioural effects that respond to endogenous and exogenous variables, it follows then that fatigue assessment techniques ought to include multi-dimensional measures to acquire a holistic depiction of the fatigue symptom. This study aimed to assess whether or not a mechanism that regulated fatigue during sustained task execution could be identified and whether this mechanism resulted in regulation patterns that were distinct to a specific task. An additional aim of the study was on assessing whether the manner in which performance, psychophysical and subjective variables were modified over time followed a similar regulation pattern. The research design was aimed at inducing task-related fatigue twice on two different occasions in the same participants and evaluating the resultant changes in fatigue manifestation. This was done to assess the ability of participants to cope with fatigue as a result of previous experience. The research protocol included three tasks executed for an hour aimed at targeting and taxing the sensory, cognitive, motor resources, each task performed twice. 60 participants were recruited to participate in the current study, with 20 participants – 10 males and 10 females – randomly assigned to each of the three tasks. The cognitive resource task consisted of a memory recall task relying on working memory intended to evaluate the extent of reductions in memory and attention. The sensory resource task consisted of a reading task measuring visual scanning and perception designed to evaluate the extent of reduced vigilance. The motor resource task consisted of a modified Fitts’ stimulus response task targeted at monitoring the extent of movement timing disruption. Performance measures comprised of: response delay and the number of correctly identified digits during the cognitive resource task, the amount of correctly identified errors and reading speed during the sensory resource task, response time during the motor resource task, and responses to simple auditory reaction time tests (RTT) initiated at intervals during the task and then again at the end of each task. Physiological measures included ear temperature, eye blink frequency and duration, heart rate (HR), and heart rate variability (HRV). Subjective measures included the use of the Ratings of Perceived Exertion Category Ratio 10 scale (RPE CR 10) to measure cognitive exertion and the NASA-Task Load Index (NASA-TLX) to index mental workload. Eye blink frequency and duration, HR and HRV were sensitive to the type of task executed, showing differing response patterns both over the different tasks and over the two test sessions. The subjective measures indicated increasing RPE ratings over time in all tasks while the NASA-TLX indicated that each task elicited different workloads. Differing task performance responses were measured between the 1st test session and the 2nd test session during all tasks; while performance was found to improve during the 2nd test session for the motor and sensory tasks, it declined during the cognitive task. The findings of this research indicate that there was a regulatory mechanism for fatigue that altered the manner in which performance, psychophysical and subjective variables were modified over time, initiating a unique fatigue regulation pattern for each variable and each task. This regulation mechanism is understood to be a proactive and protective mechanism that functions through reducing a person’s ability to be vigilant, attentive, to exercise discernment, and to direct their level of responsiveness, essentially impacting how the body adapts to and copes with fatigue. The noted overall findings have industry implications; industries should consider accounting for the effects of this regulatory mechanism in their fatigue management interventions, specifically when designing job rotation and work/rest schedules because each cognitive task, having elicited a unique fatigue regulation pattern, ought to also have a different management program. , Microsoft� Office Word 2007 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Tau, Sethunya Harriet Hlobisa
- Date: 2013 , 2013-10-11
- Subjects: Work -- Physiological aspects , Work -- Psychological aspects , Fatigue , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Employees -- Workload , Performance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5140 , http://hdl.handle.net/10962/d1006806 , Work -- Physiological aspects , Work -- Psychological aspects , Fatigue , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Employees -- Workload , Performance
- Description: Fatigue is a state that, although researched for many years, is still not completely understood. Alongside this lack of a general understanding of fatigue is a lack of knowledge on the processes involved in the regulation of fatigue. The existing theories relating to regulation are focussed on mental effort regulation, suggesting that performance outcomes are co-ordinated by effort regulation that functions by making alterations to physiological processes and strategic adjustments at a cognitive level in response to cognitive demands and goals. Since fatigue is a multi-dimensional construct with psychological, physiological, and behavioural effects that respond to endogenous and exogenous variables, it follows then that fatigue assessment techniques ought to include multi-dimensional measures to acquire a holistic depiction of the fatigue symptom. This study aimed to assess whether or not a mechanism that regulated fatigue during sustained task execution could be identified and whether this mechanism resulted in regulation patterns that were distinct to a specific task. An additional aim of the study was on assessing whether the manner in which performance, psychophysical and subjective variables were modified over time followed a similar regulation pattern. The research design was aimed at inducing task-related fatigue twice on two different occasions in the same participants and evaluating the resultant changes in fatigue manifestation. This was done to assess the ability of participants to cope with fatigue as a result of previous experience. The research protocol included three tasks executed for an hour aimed at targeting and taxing the sensory, cognitive, motor resources, each task performed twice. 60 participants were recruited to participate in the current study, with 20 participants – 10 males and 10 females – randomly assigned to each of the three tasks. The cognitive resource task consisted of a memory recall task relying on working memory intended to evaluate the extent of reductions in memory and attention. The sensory resource task consisted of a reading task measuring visual scanning and perception designed to evaluate the extent of reduced vigilance. The motor resource task consisted of a modified Fitts’ stimulus response task targeted at monitoring the extent of movement timing disruption. Performance measures comprised of: response delay and the number of correctly identified digits during the cognitive resource task, the amount of correctly identified errors and reading speed during the sensory resource task, response time during the motor resource task, and responses to simple auditory reaction time tests (RTT) initiated at intervals during the task and then again at the end of each task. Physiological measures included ear temperature, eye blink frequency and duration, heart rate (HR), and heart rate variability (HRV). Subjective measures included the use of the Ratings of Perceived Exertion Category Ratio 10 scale (RPE CR 10) to measure cognitive exertion and the NASA-Task Load Index (NASA-TLX) to index mental workload. Eye blink frequency and duration, HR and HRV were sensitive to the type of task executed, showing differing response patterns both over the different tasks and over the two test sessions. The subjective measures indicated increasing RPE ratings over time in all tasks while the NASA-TLX indicated that each task elicited different workloads. Differing task performance responses were measured between the 1st test session and the 2nd test session during all tasks; while performance was found to improve during the 2nd test session for the motor and sensory tasks, it declined during the cognitive task. The findings of this research indicate that there was a regulatory mechanism for fatigue that altered the manner in which performance, psychophysical and subjective variables were modified over time, initiating a unique fatigue regulation pattern for each variable and each task. This regulation mechanism is understood to be a proactive and protective mechanism that functions through reducing a person’s ability to be vigilant, attentive, to exercise discernment, and to direct their level of responsiveness, essentially impacting how the body adapts to and copes with fatigue. The noted overall findings have industry implications; industries should consider accounting for the effects of this regulatory mechanism in their fatigue management interventions, specifically when designing job rotation and work/rest schedules because each cognitive task, having elicited a unique fatigue regulation pattern, ought to also have a different management program. , Microsoft� Office Word 2007 , Adobe Acrobat 9.54 Paper Capture Plug-in
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An empirical investigation into task aversion
- Authors: Sunshine, Megan
- Date: 2013 , 2013-07-25
- Subjects: Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5138 , http://hdl.handle.net/10962/d1006085 , Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Description: Aversion is a complex phenomenon that arises over time through performance of cognitively demanding tasks and has been associated with the mechanisms of mental fatigue and compensatory control. However, little is known about this sensation to dissociate from the task at hand and the causation thereof. It is apparent that aversion is a negative state for the operator and could result in decreased performance and productivity. Through identification of factors that contribute to aversion when performing cognitively demanding tasks, recommendations to reduce design deficits may be employed to promote worker wellbeing and further advance performance and productivity. The current study examined possible factors that may influence aversion experienced through execution of cognitive tasks. A subsequent aim of this study was to assess a possible cause of aversion. The cause of aversion was hypothesized to be related to efficiency, namely the perception of efficiency when performing tasks and actual efficiency calculated through performance of tasks in relation to the expenditure of effort. Four investigations were undertaken with a non-repeated design between investigations and a repeated design within investigations. The first investigation was an analysis of the effect that stimulus cycling had on the aversion experienced. This consisted of a proof reading task with two conditions varying in the repetitiveness of the text, therefore, allowing an analysis as to how aversion is altered by the provision of a new stimulus to the participants. Investigation two investigated the effect that task difficulty imposed on aversion experienced. This comprised of two conditions with varied difficulty that were implemented through a driving simulator tracking task with difficulty altered by the width of the driving lane. The effect of performance feedback on the aversion experienced towards a task was the focus of the third investigation. The effect on aversion experienced was assessed through a driving simulator tracking task with a condition providing feedback of performance to participants and a condition with no knowledge of performance. The final experiment evaluated the effect of task alternations on aversion. This experiment was conducted through alternations between a driving simulator tracking task and a choice reaction task. The choice reaction tasks required participants to identify critical and non-critical stimulus. Four conditions were required for this experiment and were made up of two conditions where there was provision of alternation that varied in frequencies between the two tasks (medium alternation condition and fast alternation condition) and two conditions where no alternations were instated (driving simulator task condition and choice reaction task condition). Separations between all testing conditions were three or more days apart with sixty participants distributed between the investigations. Test duration of each condition was 30 minutes. Subjective data was recorded throughout investigations for all conditions in the form of aversion, subjectively perceived efficiency and rate of perceived exertion. Objective data was collected in the form of physiological responses and performance of tasks for the analysis of objective efficiency. For factors influencing aversion analysis, no differences in aversion experienced were found for the task difficulty and performance feedback investigations. Aversion was found to be less for the changes imposed through the task cycles and task alternation investigations. This concludes that aversion is aggravated through monotonous tasks and by a change of the stimulus or the structure of the cognitive tasks provided to operators; aversion can be alleviated. The results for the cause of aversion analysis found no difference in objective efficiency over time, with a subsequent decrease in perceived efficiency associated with the increasing aversion. Inference from these findings suggest that aversion cannot be attributed to objective inefficiency of task performance, however it can further be assumed that perception of actual efficiency is inaccurate. Perception of efficiency however had a large influence on the sensation of aversion. Aversion is seen to be more of a product of time on task, however whether this is mechanism of fatigue or compensatory control is still to be determined.
- Full Text:
- Authors: Sunshine, Megan
- Date: 2013 , 2013-07-25
- Subjects: Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5138 , http://hdl.handle.net/10962/d1006085 , Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Description: Aversion is a complex phenomenon that arises over time through performance of cognitively demanding tasks and has been associated with the mechanisms of mental fatigue and compensatory control. However, little is known about this sensation to dissociate from the task at hand and the causation thereof. It is apparent that aversion is a negative state for the operator and could result in decreased performance and productivity. Through identification of factors that contribute to aversion when performing cognitively demanding tasks, recommendations to reduce design deficits may be employed to promote worker wellbeing and further advance performance and productivity. The current study examined possible factors that may influence aversion experienced through execution of cognitive tasks. A subsequent aim of this study was to assess a possible cause of aversion. The cause of aversion was hypothesized to be related to efficiency, namely the perception of efficiency when performing tasks and actual efficiency calculated through performance of tasks in relation to the expenditure of effort. Four investigations were undertaken with a non-repeated design between investigations and a repeated design within investigations. The first investigation was an analysis of the effect that stimulus cycling had on the aversion experienced. This consisted of a proof reading task with two conditions varying in the repetitiveness of the text, therefore, allowing an analysis as to how aversion is altered by the provision of a new stimulus to the participants. Investigation two investigated the effect that task difficulty imposed on aversion experienced. This comprised of two conditions with varied difficulty that were implemented through a driving simulator tracking task with difficulty altered by the width of the driving lane. The effect of performance feedback on the aversion experienced towards a task was the focus of the third investigation. The effect on aversion experienced was assessed through a driving simulator tracking task with a condition providing feedback of performance to participants and a condition with no knowledge of performance. The final experiment evaluated the effect of task alternations on aversion. This experiment was conducted through alternations between a driving simulator tracking task and a choice reaction task. The choice reaction tasks required participants to identify critical and non-critical stimulus. Four conditions were required for this experiment and were made up of two conditions where there was provision of alternation that varied in frequencies between the two tasks (medium alternation condition and fast alternation condition) and two conditions where no alternations were instated (driving simulator task condition and choice reaction task condition). Separations between all testing conditions were three or more days apart with sixty participants distributed between the investigations. Test duration of each condition was 30 minutes. Subjective data was recorded throughout investigations for all conditions in the form of aversion, subjectively perceived efficiency and rate of perceived exertion. Objective data was collected in the form of physiological responses and performance of tasks for the analysis of objective efficiency. For factors influencing aversion analysis, no differences in aversion experienced were found for the task difficulty and performance feedback investigations. Aversion was found to be less for the changes imposed through the task cycles and task alternation investigations. This concludes that aversion is aggravated through monotonous tasks and by a change of the stimulus or the structure of the cognitive tasks provided to operators; aversion can be alleviated. The results for the cause of aversion analysis found no difference in objective efficiency over time, with a subsequent decrease in perceived efficiency associated with the increasing aversion. Inference from these findings suggest that aversion cannot be attributed to objective inefficiency of task performance, however it can further be assumed that perception of actual efficiency is inaccurate. Perception of efficiency however had a large influence on the sensation of aversion. Aversion is seen to be more of a product of time on task, however whether this is mechanism of fatigue or compensatory control is still to be determined.
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An investigation into control mechanisms of driving performance : resource depletion and effort-regulation
- Authors: Louw, Tyron Linton
- Date: 2013
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5101 , http://hdl.handle.net/10962/d1001842 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Description: Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand
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- Authors: Louw, Tyron Linton
- Date: 2013
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5101 , http://hdl.handle.net/10962/d1001842 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Description: Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand
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Changes in muscle recruitment, functional strength and ratings of perceived effort during an 8-over bowling spell: impact on performance
- Authors: Barford, Gareth Charles
- Date: 2013
- Subjects: Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5102 , http://hdl.handle.net/10962/d1003926 , Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Description: Background: The musculoskeletal demands placed on the lower limb musculature of fast bowlers over time have not received much attention. In particular, measures of muscle recruitment changes have, to the author’s knowledge, not been considered. Objective: The present study, therefore sought to establish any associations between an eight over, simulated fast bowling spell, and muscle activation patterns, power output, perceptual demands, and changes in performance. This will enable improvements in the development of training programmes. Methods: Players’ were required to attend two sessions in total. The purpose of the initial session was to collect specific demographic, anthropometric and physiological data and injury history information from each player. In addition, this first session allowed for habituation with the treadmill, the jump meter and all other equipment involved in experimentation. The second testing session involved electrode attachment sites being identified on player’s dominant leg. The areas were then shaved, wiped with an alcohol swab and left to dry, to ensure good connectivity. Pre- and post- measures of muscle activity and functional strength of the lower limbs were recorded in the Department of Human Kinetics and Ergonomics. The protocol took place at the Kingswood High Performance Centre, which is in close proximity to the initial testing site. The protocol involved players bowling eight overs (48 balls). During the protocol, accuracy, ball release speed and perceptual measures were recorded at the end of each over. After the protocol, players were driven back to the Human Kinetics and Ergonomics Department where post-testing measures were completed. The dependable variables of interest were muscle activation, functional strength of the lower limbs, ‘local’ ratings of perceived exertion (RPE), body discomfort, accuracy, and ball release speed. Results: For all muscles it was shown that, as the speed increased so did the muscle activity in players’ lower limbs. There were no significant changes in muscle activity preversus post-protocol. There was however, a general trend of decreasing muscle activity post protocol at higher testing speeds. There were significant (p<0.05) decreases in peak power following the simulated eight over bowling spell. ‘Local’ RPE displayed a significant (P<0.05) increase with each additional over and were observed to reach the ‘heavy’ category. The players’ highest discomfort area was in the lower back, with 13 players perceiving discomfort in this region following the eight over spell. The shoulder and chest were another two areas player’s indicated discomfort with eight players selecting the dominant shoulder. Seven players complained of the dominant side pectoral muscle, leading foot and dominant latissimus dorsi muscle being uncomfortable. Interestingly, the dominant pectoral showed the highest body discomfort ratings amongst players. There were no significant changes in accuracy between overs although there were large interindividual differences in accuracy points between players. The decrease in ball release speed observed during over seven was shown to be significantly (p<0.05) lower than overs one to four. Conclusion: The power output and perceived strain results of the players, appears to indicate the presence of fatigue in players. However, the results are not conclusive, as the fatigue was not shown in muscle recruitment patterns, as well as the body discomfort ratings. There was a non-significant trend observed in the lower limb muscle activation decreasing at higher speeds. Players were able to maintain accuracy. However, the significantly lower ball release speed observed during over seven showed players performance decreasing.
- Full Text:
- Authors: Barford, Gareth Charles
- Date: 2013
- Subjects: Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5102 , http://hdl.handle.net/10962/d1003926 , Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Description: Background: The musculoskeletal demands placed on the lower limb musculature of fast bowlers over time have not received much attention. In particular, measures of muscle recruitment changes have, to the author’s knowledge, not been considered. Objective: The present study, therefore sought to establish any associations between an eight over, simulated fast bowling spell, and muscle activation patterns, power output, perceptual demands, and changes in performance. This will enable improvements in the development of training programmes. Methods: Players’ were required to attend two sessions in total. The purpose of the initial session was to collect specific demographic, anthropometric and physiological data and injury history information from each player. In addition, this first session allowed for habituation with the treadmill, the jump meter and all other equipment involved in experimentation. The second testing session involved electrode attachment sites being identified on player’s dominant leg. The areas were then shaved, wiped with an alcohol swab and left to dry, to ensure good connectivity. Pre- and post- measures of muscle activity and functional strength of the lower limbs were recorded in the Department of Human Kinetics and Ergonomics. The protocol took place at the Kingswood High Performance Centre, which is in close proximity to the initial testing site. The protocol involved players bowling eight overs (48 balls). During the protocol, accuracy, ball release speed and perceptual measures were recorded at the end of each over. After the protocol, players were driven back to the Human Kinetics and Ergonomics Department where post-testing measures were completed. The dependable variables of interest were muscle activation, functional strength of the lower limbs, ‘local’ ratings of perceived exertion (RPE), body discomfort, accuracy, and ball release speed. Results: For all muscles it was shown that, as the speed increased so did the muscle activity in players’ lower limbs. There were no significant changes in muscle activity preversus post-protocol. There was however, a general trend of decreasing muscle activity post protocol at higher testing speeds. There were significant (p<0.05) decreases in peak power following the simulated eight over bowling spell. ‘Local’ RPE displayed a significant (P<0.05) increase with each additional over and were observed to reach the ‘heavy’ category. The players’ highest discomfort area was in the lower back, with 13 players perceiving discomfort in this region following the eight over spell. The shoulder and chest were another two areas player’s indicated discomfort with eight players selecting the dominant shoulder. Seven players complained of the dominant side pectoral muscle, leading foot and dominant latissimus dorsi muscle being uncomfortable. Interestingly, the dominant pectoral showed the highest body discomfort ratings amongst players. There were no significant changes in accuracy between overs although there were large interindividual differences in accuracy points between players. The decrease in ball release speed observed during over seven was shown to be significantly (p<0.05) lower than overs one to four. Conclusion: The power output and perceived strain results of the players, appears to indicate the presence of fatigue in players. However, the results are not conclusive, as the fatigue was not shown in muscle recruitment patterns, as well as the body discomfort ratings. There was a non-significant trend observed in the lower limb muscle activation decreasing at higher speeds. Players were able to maintain accuracy. However, the significantly lower ball release speed observed during over seven showed players performance decreasing.
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Selected physiological and perceptual responses of batsmen during a simulated one day international century : impact on performance
- Authors: Pote, Lee
- Date: 2013 , 2013-04-02
- Subjects: Cricket -- Batting , Sports -- Physiological aspects , Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5097 , http://hdl.handle.net/10962/d1001650
- Description: Background: Very few studies have examined the demands of prolonged batting on physical, psychophysical and performance responses. Objective: The purpose of this study was therefore to determine the physiological and perceptual responses of batsmen scoring a simulated One Day International century. Furthermore, the impact that these responses had on batting performance were also measured. Methods: Seventeen male cricketers currently playing for Rhodes University or the country districts side, performed a simulated bating innings (BATEX©), typical of scoring a One Day international century. The BATEX© protocol consisted of six, five over stages (21 minutes each), with each stage matched to a specific phase of play where batsmen were encouraged to bat with the mindset of that phase. During stages one, three and five players ran at a “self-selected cruise pace” whereas during stages two, four and six players were required to run at maximum speed. At set intervals, selected physiological, perceptual and performance measures were recorded. Results: Most physiological responses increased and decreased accordingly with the low and high intensity stages with the exception of respiratory exchange ratio and core temperature responses. Mean physiological responses however, showed a progressive rise over time. Central ratings of perceived exertion increased as a function of intensity and duration. Sprint times got slower as the protocol progressed, while accuracy (impact accuracy) improved significantly (p<0.05) after stage one and then stabilised for the remainder of the protocol. Conclusion: The simulated batting protocol significantly impacted the physiological and perceptual responses over time. This was due to both the intensity and the duration of the work-bout. Furthermore, the increased physiological load placed on the batsmen significantly impacted the physical performance of the batsmen. An increase in sprint times (players getting slower) towards the end of the protocol may indicate the presence of physical fatigue. This physical fatigue did not however seem to impact the batsmen cognitively as accuracy improved after the first stage and then remained constant over time.
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- Authors: Pote, Lee
- Date: 2013 , 2013-04-02
- Subjects: Cricket -- Batting , Sports -- Physiological aspects , Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5097 , http://hdl.handle.net/10962/d1001650
- Description: Background: Very few studies have examined the demands of prolonged batting on physical, psychophysical and performance responses. Objective: The purpose of this study was therefore to determine the physiological and perceptual responses of batsmen scoring a simulated One Day International century. Furthermore, the impact that these responses had on batting performance were also measured. Methods: Seventeen male cricketers currently playing for Rhodes University or the country districts side, performed a simulated bating innings (BATEX©), typical of scoring a One Day international century. The BATEX© protocol consisted of six, five over stages (21 minutes each), with each stage matched to a specific phase of play where batsmen were encouraged to bat with the mindset of that phase. During stages one, three and five players ran at a “self-selected cruise pace” whereas during stages two, four and six players were required to run at maximum speed. At set intervals, selected physiological, perceptual and performance measures were recorded. Results: Most physiological responses increased and decreased accordingly with the low and high intensity stages with the exception of respiratory exchange ratio and core temperature responses. Mean physiological responses however, showed a progressive rise over time. Central ratings of perceived exertion increased as a function of intensity and duration. Sprint times got slower as the protocol progressed, while accuracy (impact accuracy) improved significantly (p<0.05) after stage one and then stabilised for the remainder of the protocol. Conclusion: The simulated batting protocol significantly impacted the physiological and perceptual responses over time. This was due to both the intensity and the duration of the work-bout. Furthermore, the increased physiological load placed on the batsmen significantly impacted the physical performance of the batsmen. An increase in sprint times (players getting slower) towards the end of the protocol may indicate the presence of physical fatigue. This physical fatigue did not however seem to impact the batsmen cognitively as accuracy improved after the first stage and then remained constant over time.
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South African anthropometric dimensions for the design of an ergonomic office chair
- Authors: Korte, Janice
- Date: 2013 , 2013-09-05
- Subjects: Design -- Human factors , Office chairs , Chair design , Human engineering , Sitting position
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5137 , http://hdl.handle.net/10962/d1006046 , Design -- Human factors , Office chairs , Chair design , Human engineering , Sitting position
- Description: Office chairs are becoming a modern status symbol in the workplace. Many individuals are seated on office chairs for most of the working day. As a result of using poorly designed chairs injury and discomfort are frequently experienced, most particularly lower back pain. Correct design of chairs is imperative, and must be user-centered. The aim of this investigation has been to gather anthropometric dimensions characteristic of the South African population, as this information has not been widely assimilated to date. Once collated, this information could be used in the design of an ergonomically correct office chair, suitable for the unique characteristics of the South African working population. Anthropometric dimensions were collected from 683 South Africans (comprising 448 South African females and 235 South African males) from pre-selected companies in major centres in South Africa (Johannesburg, Pietermaritzburg, Durban, East London, Grahamstown, Port Elizabeth and Cape Town). Measurements included participants’ personal information (age, sex, home language and ethnic group), basic anthropometric measures (stature, shoulder height, mass, and waist and hip circumference) as well as specific measures of fit of the individual to the specially designed, adjustable chair. Of the 448 females, 317 were Black females, 77 were White females, 35 were Coloured females and 19 were Indian/Asian females. Of the 235 males, 112 were Black males, 79 were White males, 26 were Coloured males and 18 were Indian/Asian males. Office chair dimensions for each ethnic group were represented and differences were noted. A comparison between a current office chair’s dimensions and the South African sample office chair’s dimensions indicated modifications that would need to be constructed to suit the South African sample. The conventional office chair is still the most widely accepted office chair due to its stability and support structures that maintain the correct sitting posture of the user. An ergonomic office chair needs to incorporate anthropometric dimensions worldwide.
- Full Text:
- Authors: Korte, Janice
- Date: 2013 , 2013-09-05
- Subjects: Design -- Human factors , Office chairs , Chair design , Human engineering , Sitting position
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5137 , http://hdl.handle.net/10962/d1006046 , Design -- Human factors , Office chairs , Chair design , Human engineering , Sitting position
- Description: Office chairs are becoming a modern status symbol in the workplace. Many individuals are seated on office chairs for most of the working day. As a result of using poorly designed chairs injury and discomfort are frequently experienced, most particularly lower back pain. Correct design of chairs is imperative, and must be user-centered. The aim of this investigation has been to gather anthropometric dimensions characteristic of the South African population, as this information has not been widely assimilated to date. Once collated, this information could be used in the design of an ergonomically correct office chair, suitable for the unique characteristics of the South African working population. Anthropometric dimensions were collected from 683 South Africans (comprising 448 South African females and 235 South African males) from pre-selected companies in major centres in South Africa (Johannesburg, Pietermaritzburg, Durban, East London, Grahamstown, Port Elizabeth and Cape Town). Measurements included participants’ personal information (age, sex, home language and ethnic group), basic anthropometric measures (stature, shoulder height, mass, and waist and hip circumference) as well as specific measures of fit of the individual to the specially designed, adjustable chair. Of the 448 females, 317 were Black females, 77 were White females, 35 were Coloured females and 19 were Indian/Asian females. Of the 235 males, 112 were Black males, 79 were White males, 26 were Coloured males and 18 were Indian/Asian males. Office chair dimensions for each ethnic group were represented and differences were noted. A comparison between a current office chair’s dimensions and the South African sample office chair’s dimensions indicated modifications that would need to be constructed to suit the South African sample. The conventional office chair is still the most widely accepted office chair due to its stability and support structures that maintain the correct sitting posture of the user. An ergonomic office chair needs to incorporate anthropometric dimensions worldwide.
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The factors affecting self-regulation through the analysis of physiological, psychological and behavioural measures during task-switching
- Authors: Chaplin, Caley
- Date: 2013 , 2013-07-16
- Subjects: Human multitasking -- Physiological aspects , Human multitasking -- Psychological aspects , Fatigue , Boredom , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Industrial hygiene , Employees -- Workload
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5135 , http://hdl.handle.net/10962/d1006027 , Human multitasking -- Physiological aspects , Human multitasking -- Psychological aspects , Fatigue , Boredom , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Industrial hygiene , Employees -- Workload
- Description: Individuals are required to manage multiple tasks which require strategic allocation of time and effort to ensure goals are reached efficiently. By providing the worker with autonomy over their work, performance and worker well-being have improved. This increased control allows individuals to organize work according to the needs of the body, which prevents fatigue leading to improved productivity. When given the option, humans tend to switch between tasks frequently. This behaviour can be used to determine the change in self-regulation strategies. An understanding of human task-switching behaviour is important for the design of job rotation systems. However, there is a lack of evidence explaining the factors motivating the need to switch between tasks. This study aims to use physiological, subjective and behavioural measures to explain the factors influencing selfregulation through the act of task-switching. Three primary hypotheses were developed to explain the factors underlying taskswitching behaviour. It was hypothesized that the degree of boredom experienced, the effort required to perform the task and the resource usage induced by the task are factors responsible in deciding task switching behaviour. Participants (17 males and 17 females) switched freely between five different information-processing tasks for the 45 minutes. Participants were allowed to switch back and forth between tasks and did not have to conduct all five tasks. The following measures were recorded during the experiment: subjective measures of boredom, mental effort, task frustration and perceived performance of the tasks; energy consumption and physiological measures of effort (HR, HRV and body temperature) and behavioural measures, including duration and frequency of task. Perceived boredom was found to differ among the tasks and before and after the experiment. The average boredom rating at each task transition for all tasks exceeded a score of 2.5 out of a possible 4. There were no significant changes in physiological measures between the beginning and end of the task trials. However, changes in physiological measures showed a decrease in effort investment following task transition. Heart rate variability was lower for externally-paced tasks than for self-paced tasks, despite the differences in cognitive demands. The most frequent task-switch combination occurred between tasks of high and low cognitive demand. The least frequent task-switching combination occurred between tasks of similar characteristics, which produced no differences in physiological responses. Task-switching behaviour was influenced by the degree of boredom, and therefore more time was spent on less monotonous tasks. The level of physiological effort required for the task affected task-switching behaviour. Task switches were made before any changes in effort took place in an attempt to maintain task efficiency. It appears plausible that a task switch was made to reduce effort investment and activation levels. The type of information processing resources used by different tasks affected the task-switching combinations. Individuals tended to switch between tasks of differing resources so that those in limited supply were able to replenish. Therefore the findings from this study can potentially be used to improve the design of job rotation systems. Such improvements may enhance productivity and worker well-being by inhibiting the onset of down regulation and fatigue processes. This study showed that autonomy is necessary for individuals to regulate behaviour to suit human needs. , Microsoft� Office Word 2007 , Adobe Acrobat 9.54 Paper Capture Plug-in
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- Authors: Chaplin, Caley
- Date: 2013 , 2013-07-16
- Subjects: Human multitasking -- Physiological aspects , Human multitasking -- Psychological aspects , Fatigue , Boredom , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Industrial hygiene , Employees -- Workload
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5135 , http://hdl.handle.net/10962/d1006027 , Human multitasking -- Physiological aspects , Human multitasking -- Psychological aspects , Fatigue , Boredom , Attention , Mental fatigue , Human information processing , Decision making , Labor productivity , Industrial hygiene , Employees -- Workload
- Description: Individuals are required to manage multiple tasks which require strategic allocation of time and effort to ensure goals are reached efficiently. By providing the worker with autonomy over their work, performance and worker well-being have improved. This increased control allows individuals to organize work according to the needs of the body, which prevents fatigue leading to improved productivity. When given the option, humans tend to switch between tasks frequently. This behaviour can be used to determine the change in self-regulation strategies. An understanding of human task-switching behaviour is important for the design of job rotation systems. However, there is a lack of evidence explaining the factors motivating the need to switch between tasks. This study aims to use physiological, subjective and behavioural measures to explain the factors influencing selfregulation through the act of task-switching. Three primary hypotheses were developed to explain the factors underlying taskswitching behaviour. It was hypothesized that the degree of boredom experienced, the effort required to perform the task and the resource usage induced by the task are factors responsible in deciding task switching behaviour. Participants (17 males and 17 females) switched freely between five different information-processing tasks for the 45 minutes. Participants were allowed to switch back and forth between tasks and did not have to conduct all five tasks. The following measures were recorded during the experiment: subjective measures of boredom, mental effort, task frustration and perceived performance of the tasks; energy consumption and physiological measures of effort (HR, HRV and body temperature) and behavioural measures, including duration and frequency of task. Perceived boredom was found to differ among the tasks and before and after the experiment. The average boredom rating at each task transition for all tasks exceeded a score of 2.5 out of a possible 4. There were no significant changes in physiological measures between the beginning and end of the task trials. However, changes in physiological measures showed a decrease in effort investment following task transition. Heart rate variability was lower for externally-paced tasks than for self-paced tasks, despite the differences in cognitive demands. The most frequent task-switch combination occurred between tasks of high and low cognitive demand. The least frequent task-switching combination occurred between tasks of similar characteristics, which produced no differences in physiological responses. Task-switching behaviour was influenced by the degree of boredom, and therefore more time was spent on less monotonous tasks. The level of physiological effort required for the task affected task-switching behaviour. Task switches were made before any changes in effort took place in an attempt to maintain task efficiency. It appears plausible that a task switch was made to reduce effort investment and activation levels. The type of information processing resources used by different tasks affected the task-switching combinations. Individuals tended to switch between tasks of differing resources so that those in limited supply were able to replenish. Therefore the findings from this study can potentially be used to improve the design of job rotation systems. Such improvements may enhance productivity and worker well-being by inhibiting the onset of down regulation and fatigue processes. This study showed that autonomy is necessary for individuals to regulate behaviour to suit human needs. , Microsoft� Office Word 2007 , Adobe Acrobat 9.54 Paper Capture Plug-in
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The impact of low to moderate alcohol consumption on different types of human performance
- Authors: Goble, David
- Date: 2013
- Subjects: Alcohol -- Physiological effect Temperance Human information processing -- Effect of drugs on Visual perception -- Effect of drugs on Cognition -- Effect of drugs on Caffeine -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5136 , http://hdl.handle.net/10962/d1006042
- Description: Despite extensive research into the effects of alcohol consumption, there is no clear understanding into the mechanisms underlying human information processing impairment. The acute consumption of alcohol was investigated to determine the implications for human information processing capabilities, and to identify the extent to which these implications were stage-specific. Further aims included the investigation and quantification of caffeine-induced antagonism of alcohol impairment. Moreover, the aforementioned relationships were investigated in morning versus evening conditions. A test battery of six resource-specific tasks was utilised to measure visual perceptual, cognitive and sensory-motor performance, fashioned to return both simple and complex measures of each task. The tasks implemented were: visual perceptual performance (accommodation, visual detection, visual pattern recognition); cognition (memory recall- digit span); and motor output (modified Fitts‟ and a driving simulated line-tracking). Performance measures were recorded by the respective computer based tasks. Physiological variables measured included heart rate frequency, heart rate variability (RMSSD, High and Low Frequency Power) and body temperature. Saccade speed, saccade amplitude, pupil size and fixation duration were the oculomotor parameters measured. Three groups of participants (alcohol, caffeine+alcohol and control) n=36 were studied, split evenly between sexes in a mixed repeated/non-repeated measures design. The control group performed all test batteries under no influence. The alcohol group performed test batteries one and two sober, and three and four under the influence of a 0.4 g/kg dose of alcohol. Group caffeine+alcohol conducted test battery one sober, two under the effect of caffeine only (4 mg/kg), and three and four under the influence of both caffeine and alcohol (0.4 g/kg). The third test battery demonstrated the effects of alcohol during the inclining phase of the blood alcohol curve, and the fourth represented the declining phase. Morning experimentation occurred between 10:00 - 12: 45 and 10:30 -13:15 with evening experimentation between 19:00 - 21:30 and 19:30 - 22:00. Acute alcohol consumption at a dose of approximately 0.4 g/kg body weight effected an average peak breath alcohol concentration of 0.062 % and 0.059 % for the alcohol and caffeine+alcohol groups respectively. Task-related visual perceptual performance demonstrated significant decrements for simple reaction time, choice reaction time and error rate. Cognitive performance demonstrated no significant performance decrements, while motor performance indicated significant decrements in target accuracy only. Physiological parameters in response to alcohol consumption showed significantly decreased heart rate variability (RMSSD) in the modified Fitts‟ task only. A significant decrease in saccade amplitude in the memory task was the only change in oculomotor parameters. Prior caffeine consumption demonstrated limited antagonism to task-related alcohol impairment, significantly improving performance only in reduced error rate while reading. Caffeine consumption showed stimulating effects on physiological parameters, significantly increasing heart rate and heart rate variability when compared to alcohol alone. The design of the tasks allows for comparison between complex and simple task performance, indicating resource utilisation and depletion. Complex tasks demonstrated higher resource utilisation, however with no statistical performance differences to simple tasks. Physiological parameters showed greater change in response to alcohol consumption, than did the performance measures. Alcohol consumption imposed significant changes in physiological and oculomotor parameters for cognitive tasks only, significantly increasing heart rate frequency and decreasing heart rate variability, skin temperature and saccade amplitude. Caffeine consumption showed no antagonism of alcohol-induced performance measures. Physiological measures showed that caffeine consumption imposed stimulating effects in only the neural reflex and memory tasks, significantly increasing heart rate frequency and heart rate variability. Prior caffeine consumption significantly decreased fixation duration in the memory task only. The time of day at which alcohol was consumed demonstrated significant performance and physiological implications. Results indicated that morning consumption of alcohol imposes greater decrements in performance and larger fluctuations in physiological parameters than the decrements in evening experimental sessions. It can be concluded that alcohol consumption at a dose of 0.4 g/kg affects all stages in the information processing chain. Task performance indicates that alcohol has a greater severity on the early stages of information processing. Conversely, under the influence of alcohol an increased task complexity induces greater effects on central stage information processing. In addition, caffeine consumption at a dose of 4 mg/kg prior to alcohol does not antagonise the alcohol-induced performance decrements.
- Full Text:
- Authors: Goble, David
- Date: 2013
- Subjects: Alcohol -- Physiological effect Temperance Human information processing -- Effect of drugs on Visual perception -- Effect of drugs on Cognition -- Effect of drugs on Caffeine -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5136 , http://hdl.handle.net/10962/d1006042
- Description: Despite extensive research into the effects of alcohol consumption, there is no clear understanding into the mechanisms underlying human information processing impairment. The acute consumption of alcohol was investigated to determine the implications for human information processing capabilities, and to identify the extent to which these implications were stage-specific. Further aims included the investigation and quantification of caffeine-induced antagonism of alcohol impairment. Moreover, the aforementioned relationships were investigated in morning versus evening conditions. A test battery of six resource-specific tasks was utilised to measure visual perceptual, cognitive and sensory-motor performance, fashioned to return both simple and complex measures of each task. The tasks implemented were: visual perceptual performance (accommodation, visual detection, visual pattern recognition); cognition (memory recall- digit span); and motor output (modified Fitts‟ and a driving simulated line-tracking). Performance measures were recorded by the respective computer based tasks. Physiological variables measured included heart rate frequency, heart rate variability (RMSSD, High and Low Frequency Power) and body temperature. Saccade speed, saccade amplitude, pupil size and fixation duration were the oculomotor parameters measured. Three groups of participants (alcohol, caffeine+alcohol and control) n=36 were studied, split evenly between sexes in a mixed repeated/non-repeated measures design. The control group performed all test batteries under no influence. The alcohol group performed test batteries one and two sober, and three and four under the influence of a 0.4 g/kg dose of alcohol. Group caffeine+alcohol conducted test battery one sober, two under the effect of caffeine only (4 mg/kg), and three and four under the influence of both caffeine and alcohol (0.4 g/kg). The third test battery demonstrated the effects of alcohol during the inclining phase of the blood alcohol curve, and the fourth represented the declining phase. Morning experimentation occurred between 10:00 - 12: 45 and 10:30 -13:15 with evening experimentation between 19:00 - 21:30 and 19:30 - 22:00. Acute alcohol consumption at a dose of approximately 0.4 g/kg body weight effected an average peak breath alcohol concentration of 0.062 % and 0.059 % for the alcohol and caffeine+alcohol groups respectively. Task-related visual perceptual performance demonstrated significant decrements for simple reaction time, choice reaction time and error rate. Cognitive performance demonstrated no significant performance decrements, while motor performance indicated significant decrements in target accuracy only. Physiological parameters in response to alcohol consumption showed significantly decreased heart rate variability (RMSSD) in the modified Fitts‟ task only. A significant decrease in saccade amplitude in the memory task was the only change in oculomotor parameters. Prior caffeine consumption demonstrated limited antagonism to task-related alcohol impairment, significantly improving performance only in reduced error rate while reading. Caffeine consumption showed stimulating effects on physiological parameters, significantly increasing heart rate and heart rate variability when compared to alcohol alone. The design of the tasks allows for comparison between complex and simple task performance, indicating resource utilisation and depletion. Complex tasks demonstrated higher resource utilisation, however with no statistical performance differences to simple tasks. Physiological parameters showed greater change in response to alcohol consumption, than did the performance measures. Alcohol consumption imposed significant changes in physiological and oculomotor parameters for cognitive tasks only, significantly increasing heart rate frequency and decreasing heart rate variability, skin temperature and saccade amplitude. Caffeine consumption showed no antagonism of alcohol-induced performance measures. Physiological measures showed that caffeine consumption imposed stimulating effects in only the neural reflex and memory tasks, significantly increasing heart rate frequency and heart rate variability. Prior caffeine consumption significantly decreased fixation duration in the memory task only. The time of day at which alcohol was consumed demonstrated significant performance and physiological implications. Results indicated that morning consumption of alcohol imposes greater decrements in performance and larger fluctuations in physiological parameters than the decrements in evening experimental sessions. It can be concluded that alcohol consumption at a dose of 0.4 g/kg affects all stages in the information processing chain. Task performance indicates that alcohol has a greater severity on the early stages of information processing. Conversely, under the influence of alcohol an increased task complexity induces greater effects on central stage information processing. In addition, caffeine consumption at a dose of 4 mg/kg prior to alcohol does not antagonise the alcohol-induced performance decrements.
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The influence of soccer-specific fatigue on the risk of thigh injuries in amateur black African players
- Authors: Jones, Robert Ian
- Date: 2013
- Subjects: Soccer injuries -- South Africa -- Eastern Cape Thigh -- Wounds and injuries -- South Africa -- Eastern Cape Hamstring muscle -- Wounds and injuries -- South Africa -- Eastern Cape Black people -- Wounds and injuries -- South Africa -- Eastern Cape Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5100 , http://hdl.handle.net/10962/d1001841
- Description: Background: Epidemiological findings indicate a higher risk of muscular thigh strain injury during the latter stages of both halves of soccer match-play, with muscular fatigue highlighted as a key etiological factor in injury causation. Anthropometric, biomechanical and physiological differences present in the Black African population may elicit unique thigh injury risk profiles, different from those of European and American players. Objectives: The purpose of the current research was to investigate the impact of soccer-specific fatigue on the risk of hamstring and quadricep injury in amateur Black African soccer players, in both the dominant and non-dominant legs. Methods: Participants were required to perform a soccer matchplay simulation (SAFT⁹⁰), consisting of multidirectional and utility movements, as well as frequent acceleration and deceleration. Selected physical, physiological and psychophysical responses were collected at specific time intervals throughout fatigue protocol performance. Results: Heart rate responses were observed to increase significantly (p<0.05) in response to the start of both halves, and remain elevated (but showing no further significant increase) during the performance of the remainder of the fatigue protocol. Significant (p<0.05) changes in both concentric and eccentric isokinetic variables of the knee flexors and extensors highlight the effect of muscular fatigue on performance in soccer match-play. Eccentric hamstring peak torque was observed to decrease significantly over time (60°.s⁻ₑ=17.34%, 180°.s⁻ₑ=18.27%), with significant reductions observed during both halves. The functional H:Q ratio at 180°.s⁻ₑ indicated a significant decrease over time (10.04%), with a significant decrease indicated during the second half of the SAFT⁹⁰ protocol. The passive half time interval did not result in significant changes in isokinetic variables. Isokinetic strength, work and power indicated no significant effects of leg dominance.. ‘Central’ and ‘Local’ ratings of exertion were observed to increase significantly (p<0.05) as a function of exercise duration. Conclusion: The overall reduction in both the eccentric hamstring peak torque and the functional strength ratio was illustrated to be similar to that of other soccer-specific fatigue research. As a result, the risk of thigh strain injuries is suggested to be similar regardless of playing level and race. These time dependent changes may have implications for competitive performance and increased predisposition to hamstring strain injuries during the latter stages of both halves of match-play
- Full Text:
- Authors: Jones, Robert Ian
- Date: 2013
- Subjects: Soccer injuries -- South Africa -- Eastern Cape Thigh -- Wounds and injuries -- South Africa -- Eastern Cape Hamstring muscle -- Wounds and injuries -- South Africa -- Eastern Cape Black people -- Wounds and injuries -- South Africa -- Eastern Cape Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5100 , http://hdl.handle.net/10962/d1001841
- Description: Background: Epidemiological findings indicate a higher risk of muscular thigh strain injury during the latter stages of both halves of soccer match-play, with muscular fatigue highlighted as a key etiological factor in injury causation. Anthropometric, biomechanical and physiological differences present in the Black African population may elicit unique thigh injury risk profiles, different from those of European and American players. Objectives: The purpose of the current research was to investigate the impact of soccer-specific fatigue on the risk of hamstring and quadricep injury in amateur Black African soccer players, in both the dominant and non-dominant legs. Methods: Participants were required to perform a soccer matchplay simulation (SAFT⁹⁰), consisting of multidirectional and utility movements, as well as frequent acceleration and deceleration. Selected physical, physiological and psychophysical responses were collected at specific time intervals throughout fatigue protocol performance. Results: Heart rate responses were observed to increase significantly (p<0.05) in response to the start of both halves, and remain elevated (but showing no further significant increase) during the performance of the remainder of the fatigue protocol. Significant (p<0.05) changes in both concentric and eccentric isokinetic variables of the knee flexors and extensors highlight the effect of muscular fatigue on performance in soccer match-play. Eccentric hamstring peak torque was observed to decrease significantly over time (60°.s⁻ₑ=17.34%, 180°.s⁻ₑ=18.27%), with significant reductions observed during both halves. The functional H:Q ratio at 180°.s⁻ₑ indicated a significant decrease over time (10.04%), with a significant decrease indicated during the second half of the SAFT⁹⁰ protocol. The passive half time interval did not result in significant changes in isokinetic variables. Isokinetic strength, work and power indicated no significant effects of leg dominance.. ‘Central’ and ‘Local’ ratings of exertion were observed to increase significantly (p<0.05) as a function of exercise duration. Conclusion: The overall reduction in both the eccentric hamstring peak torque and the functional strength ratio was illustrated to be similar to that of other soccer-specific fatigue research. As a result, the risk of thigh strain injuries is suggested to be similar regardless of playing level and race. These time dependent changes may have implications for competitive performance and increased predisposition to hamstring strain injuries during the latter stages of both halves of match-play
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Investigation of the effect of short duration breaks in delaying the onset of performance related fatigue during long distance monotonous driving at different times of the day
- Authors: Ndaki, Ntombikayise
- Date: 2012
- Subjects: Fatigue -- Physiological aspects , Drowsiness -- Physiological aspects , Automobile driving -- Physiological aspects , Traffic safety -- South Africa , Automobile driving -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5170 , http://hdl.handle.net/10962/d1016353
- Description: Road traffic accidents are a serious burden to the health systems of many countries especially in South Africa. Research aimed at reducing traffic related accidents is of importance as traffic crashes are rated as the second leading cause of fatalities in South Africa and ninth in the world. Despite the extensive efforts into research and development of new technology, driver fatigue still remains a cause of vehicle accidents worldwide. Fatigue plays a role in up to 20% of vehicle accidents with many being serious or fatal. Numerous coping behaviours are employed by drivers to counteract the negative effects of fatigue. The most common coping behaviours include taking short naps, talking to passengers, listening to the radio, opening windows and drinking stimulants. Driving breaks have long been identified as an effective countermeasure against fatigue. Most research done in driving breaks has investigated the duration of the breaks, activity undertaken during the break and the frequency of the breaks taken outside the vehicle. However limited literature is available on the effectiveness of breaks in counteracting the effects of fatigue. The objective of the current study was aimed at assessing whether short duration breaks are an effective countermeasure against fatigue. Physiological, neurophysiological, subjective and performance measures were used as indicators for fatigue. Additional focus of the research was determining whether breaks were more or less effective at counteracting the effects of fatigue at different times of day. Twelve participants were recruited for the study, six males and six females. The participants were required to perform a driving task on a simulator for 90 minutes. The study consisted of four independent conditions, namely driving during the day with breaks, driving during the day without breaks, driving during the night with breaks and driving during the night without breaks. The without breaks conditions were similar except that they occurred at different times of the day, one session at night and the other session during day time, as was the case for the conditions with breaks. The driving task used in the current study was a low fidelity simulator tracking task. The participants were required to follow a centre line displayed on a tracking path as accurately as possible. The measurements that were recorded in this study included physiological, performance, subjective and neurophysiological. Physiological measures included heart rate and heart rate variability (frequency domain) and core body temperature. The ascending threshold of the critical flicker fusion frequency was the only neurophysiological measurement included in the current investigation. Performance was quantified by mean deviation from a centre line participants were meant to track. Two rating scales were used: Karolinska sleepiness scale and the Wits sleepiness scale were used for the measurement of subjective sleepiness. Heart rate, heart rate variability and mean deviation were measured continuously throughout the 90 minute driving task. Critical flicker fusion frequency, temperature and the subjective scales were measured before and after the 90 minute driving task. The results indicated that the short duration breaks during day time had a positive effect on driving performance; however the breaks at night had a negative effect on driving performance. Heart rate was higher during the day compared to night time and the heart rate variability high frequency spectrum values were lower during the day condition, to show the activation of the sympathetic nervous system which is characteristic of day time. The night conditions had lower heart rate values and higher heart rate variability high frequency values, which show the activation of the parasympathetic nervous system which is dominant during periods of fatigue and night time. Subjective sleepiness levels were also higher at night compared to day time.
- Full Text:
- Authors: Ndaki, Ntombikayise
- Date: 2012
- Subjects: Fatigue -- Physiological aspects , Drowsiness -- Physiological aspects , Automobile driving -- Physiological aspects , Traffic safety -- South Africa , Automobile driving -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5170 , http://hdl.handle.net/10962/d1016353
- Description: Road traffic accidents are a serious burden to the health systems of many countries especially in South Africa. Research aimed at reducing traffic related accidents is of importance as traffic crashes are rated as the second leading cause of fatalities in South Africa and ninth in the world. Despite the extensive efforts into research and development of new technology, driver fatigue still remains a cause of vehicle accidents worldwide. Fatigue plays a role in up to 20% of vehicle accidents with many being serious or fatal. Numerous coping behaviours are employed by drivers to counteract the negative effects of fatigue. The most common coping behaviours include taking short naps, talking to passengers, listening to the radio, opening windows and drinking stimulants. Driving breaks have long been identified as an effective countermeasure against fatigue. Most research done in driving breaks has investigated the duration of the breaks, activity undertaken during the break and the frequency of the breaks taken outside the vehicle. However limited literature is available on the effectiveness of breaks in counteracting the effects of fatigue. The objective of the current study was aimed at assessing whether short duration breaks are an effective countermeasure against fatigue. Physiological, neurophysiological, subjective and performance measures were used as indicators for fatigue. Additional focus of the research was determining whether breaks were more or less effective at counteracting the effects of fatigue at different times of day. Twelve participants were recruited for the study, six males and six females. The participants were required to perform a driving task on a simulator for 90 minutes. The study consisted of four independent conditions, namely driving during the day with breaks, driving during the day without breaks, driving during the night with breaks and driving during the night without breaks. The without breaks conditions were similar except that they occurred at different times of the day, one session at night and the other session during day time, as was the case for the conditions with breaks. The driving task used in the current study was a low fidelity simulator tracking task. The participants were required to follow a centre line displayed on a tracking path as accurately as possible. The measurements that were recorded in this study included physiological, performance, subjective and neurophysiological. Physiological measures included heart rate and heart rate variability (frequency domain) and core body temperature. The ascending threshold of the critical flicker fusion frequency was the only neurophysiological measurement included in the current investigation. Performance was quantified by mean deviation from a centre line participants were meant to track. Two rating scales were used: Karolinska sleepiness scale and the Wits sleepiness scale were used for the measurement of subjective sleepiness. Heart rate, heart rate variability and mean deviation were measured continuously throughout the 90 minute driving task. Critical flicker fusion frequency, temperature and the subjective scales were measured before and after the 90 minute driving task. The results indicated that the short duration breaks during day time had a positive effect on driving performance; however the breaks at night had a negative effect on driving performance. Heart rate was higher during the day compared to night time and the heart rate variability high frequency spectrum values were lower during the day condition, to show the activation of the sympathetic nervous system which is characteristic of day time. The night conditions had lower heart rate values and higher heart rate variability high frequency values, which show the activation of the parasympathetic nervous system which is dominant during periods of fatigue and night time. Subjective sleepiness levels were also higher at night compared to day time.
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Musculoskeletal and perceptual responses of batsmen comparing high- and moderate-volume sprints between the wickets
- Authors: Sheppard, Bronwyn Jane
- Date: 2012
- Subjects: Cricket -- Batting -- Physiological aspects , Cricket injuries , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5171 , http://hdl.handle.net/10962/d1016366
- Description: Background: Literature has associated repeated eccentric muscle actions with increased muscle damage of the muscles involved. Eccentric actions are typical in sports which are ‘stop-start’ in nature requiring rapid acceleration and deceleration, typical of a batting activity in cricket. Ultra-structural damage of the skeletal muscle as a consequence of repeated decelerating activities is associated with performance decrements, particularly muscle strength and sprinting speeds. This suggests that eccentric strength decrements may provide an indication for the development of muscle strain injuries during these activities. Despite these findings, limited research has identified the specific musculoskeletal demands placed on cricket batsmen, particularly with reference to various match intensities. Objective: The present study, therefore, sought to determine the specific musculoskeletal, physiological and perceptual demands placed on specialised batsmen during two work bouts of different intensities; one representing a highintensity work bout and the other a moderate-intensity work bout. The dependent variables of interest were muscle activation, isokinetic strength changes, heart rate, ‘central’ and ‘local’ ratings of perceived exertion (RPE), body discomfort and performance. Methods: The two experimental conditions, representative of a high- (HVR) and moderate-volume running (MVR) batting protocol, required players to perform a simulated batting work bout of either twelve or six runs an over, within a laboratory setting. Selected physiological, perceptual and performance measures were collected at specific time intervals throughout the work bout while the biophysical measures were collected prior to, and following both protocols. Results: Of the variables measured, heart rate, ‘central’ and ‘local’ RPE values were observed to increase significantly (p<0.05) over time. This increase was greater as a consequence of the HVR in comparison to the MVR. No change in sprint times was documented during the MVR, in contrast, significant (p<0.05) increases over time were observed during the HVR, further highlighting the elevated demands associated with this condition. In addition, an ‘end spurt’ was observed particularly following the HVR condition, suggesting athletes were conserving themselves through the adoption of a pacing strategy. Reductions in biceps femoris and semitendinosus muscle activation levels were observed following the HVR. This was further supported by the significantly greater levels of semitendinosus activation following the MVR when compared to the HVR. Peak concentric and eccentric knee extensor (EXT) (-17.17% and -16.07% respectively) and eccentric flexor (FLEX) (- 17.49%) values decreased significantly (p<0.05) following the HVR at 60°.s-1. In addition, concentric and eccentric total work produced by the flexors and eccentric extensors resulted in significantly (p<0.05) lower values due to the HVR. Conclusion: The intermittent high-volume batting work bout elicited elevated mean heart rates, perceived ratings of cardiovascular and muscular effort and sprint times. Furthermore, hamstring activation levels and muscle strength, particularly concentric strength of the dominant lower limb were negatively affected by the HVR condition. These results suggest elevated demands were placed on the hamstring musculature as a consequence of the HVR condition, indicating a greater degree of musculoskeletal strain and increased injury risk associated with running between the wickets at this intensity, representative of an aggressive batting scenario.
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- Authors: Sheppard, Bronwyn Jane
- Date: 2012
- Subjects: Cricket -- Batting -- Physiological aspects , Cricket injuries , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5171 , http://hdl.handle.net/10962/d1016366
- Description: Background: Literature has associated repeated eccentric muscle actions with increased muscle damage of the muscles involved. Eccentric actions are typical in sports which are ‘stop-start’ in nature requiring rapid acceleration and deceleration, typical of a batting activity in cricket. Ultra-structural damage of the skeletal muscle as a consequence of repeated decelerating activities is associated with performance decrements, particularly muscle strength and sprinting speeds. This suggests that eccentric strength decrements may provide an indication for the development of muscle strain injuries during these activities. Despite these findings, limited research has identified the specific musculoskeletal demands placed on cricket batsmen, particularly with reference to various match intensities. Objective: The present study, therefore, sought to determine the specific musculoskeletal, physiological and perceptual demands placed on specialised batsmen during two work bouts of different intensities; one representing a highintensity work bout and the other a moderate-intensity work bout. The dependent variables of interest were muscle activation, isokinetic strength changes, heart rate, ‘central’ and ‘local’ ratings of perceived exertion (RPE), body discomfort and performance. Methods: The two experimental conditions, representative of a high- (HVR) and moderate-volume running (MVR) batting protocol, required players to perform a simulated batting work bout of either twelve or six runs an over, within a laboratory setting. Selected physiological, perceptual and performance measures were collected at specific time intervals throughout the work bout while the biophysical measures were collected prior to, and following both protocols. Results: Of the variables measured, heart rate, ‘central’ and ‘local’ RPE values were observed to increase significantly (p<0.05) over time. This increase was greater as a consequence of the HVR in comparison to the MVR. No change in sprint times was documented during the MVR, in contrast, significant (p<0.05) increases over time were observed during the HVR, further highlighting the elevated demands associated with this condition. In addition, an ‘end spurt’ was observed particularly following the HVR condition, suggesting athletes were conserving themselves through the adoption of a pacing strategy. Reductions in biceps femoris and semitendinosus muscle activation levels were observed following the HVR. This was further supported by the significantly greater levels of semitendinosus activation following the MVR when compared to the HVR. Peak concentric and eccentric knee extensor (EXT) (-17.17% and -16.07% respectively) and eccentric flexor (FLEX) (- 17.49%) values decreased significantly (p<0.05) following the HVR at 60°.s-1. In addition, concentric and eccentric total work produced by the flexors and eccentric extensors resulted in significantly (p<0.05) lower values due to the HVR. Conclusion: The intermittent high-volume batting work bout elicited elevated mean heart rates, perceived ratings of cardiovascular and muscular effort and sprint times. Furthermore, hamstring activation levels and muscle strength, particularly concentric strength of the dominant lower limb were negatively affected by the HVR condition. These results suggest elevated demands were placed on the hamstring musculature as a consequence of the HVR condition, indicating a greater degree of musculoskeletal strain and increased injury risk associated with running between the wickets at this intensity, representative of an aggressive batting scenario.
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Peripheral vision field fatigue during simulated driving : the effects of time on task and time of day on selected psychophysiological, performance and subjective responses
- Authors: Robertson, Jade Kelly
- Date: 2012 , 2012-09-22
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5141 , http://hdl.handle.net/10962/d1007136 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Description: Worldwide, motor accidents are responsible for a large number of deaths and disabilities (Connor et al., 2001), and one of the major causes of motor accidents is driver fatigue. Although majority of drivers are aware of the dangers of fatigued driving, accidents related to this continues to contribute to a large percentage of all accidents, between 5 and 50% (Nilsson et al., 1997; Williamson et al., 2011). The purpose of the research was to establish the effect that fatigue renders on an individual’s peripheral visual field and to determine whether a decrement in driving performance occurs at the same rate as a decrement in peripheral visual performance. Fatigue was induced through time of day as well as time on task. Sixteen students from Rhodes University were recruited, subject to no previous sleep disorders, among other criteria. Each participant was required to partake in two conditions, namely a day condition (09h00–11h00) and a night condition (23h00– 01h00). Each condition consisted of a 90 minute dual task; the primary task was a tracking task, in which participants were instructed to track a white line as accurately as possible. A secondary peripheral response task was introduced, in which participants were instructed to respond as quickly as possible to the peripheral stimuli, by pressing one of two clickers located on the steering wheel. The peripheral stimuli were located at 20º, 30º and 40º visual angle. Psychophysiological, performance and subjective measures were obtained before, during and after the main task. The pre- and post-tests included core body temperature, critical flicker fusion frequency threshold, a digit span memory test, Wits Sleepiness Scale and a NASA-TLX questionnaire. The psychophysiological and performance measures of heart rate, heart rate variability, blink frequency, blink duration, lane deviation, number of saccades towards peripheral stimuli, response time to peripheral stimuli and the percentage of missed peripheral responses were all recorded throughout the 90 minute main dual task. The results revealed significant differences (p<0.05) for heart rate variability, number of saccades towards peripheral stimuli and the Wits Sleepiness Scale, with regard to time of day. For time on task, significant effects were established for lane deviation, response time to peripheral stimuli, percentage of missed peripheral responses, heart rate, heart rate variability, blink frequency, blink duration, critical flicker fusion frequency threshold, core body temperature and the Wits Sleepiness Scale. Eccentricity was analysed and found to be significant for response time to peripheral stimuli, as well as for the percentage of missed peripheral responses; there was a significant increase in both measures with an increase in the stimuli eccentricity. No significances were established for time of day or between the pre- and post-tests conducted for the digit span memory performance; however, a significant interactional effect between the two was established. When assessing the percentage rate of decrement of driving performance compared to the percentage rate in the decrement of the missed peripheral responses, it was found that the percentage rate of decrement was equal for both measures. Thus from this research it can be seen that, concurrent with a decrement in driving performance, there are adverse effects on an individuals' peripheral vision, which have great implications for the safety of workers in industry and transport, as well as motorists. It was also established that time on task is possibly a more appropriate variable to consider than time of day, when implementing work schedules and rest breaks in industry, transport and fields alike, as more significant findings were seen for time on task compared to time of day. , Adobe Acrobat 9.53 Paper Capture Plug-in
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- Authors: Robertson, Jade Kelly
- Date: 2012 , 2012-09-22
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5141 , http://hdl.handle.net/10962/d1007136 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Description: Worldwide, motor accidents are responsible for a large number of deaths and disabilities (Connor et al., 2001), and one of the major causes of motor accidents is driver fatigue. Although majority of drivers are aware of the dangers of fatigued driving, accidents related to this continues to contribute to a large percentage of all accidents, between 5 and 50% (Nilsson et al., 1997; Williamson et al., 2011). The purpose of the research was to establish the effect that fatigue renders on an individual’s peripheral visual field and to determine whether a decrement in driving performance occurs at the same rate as a decrement in peripheral visual performance. Fatigue was induced through time of day as well as time on task. Sixteen students from Rhodes University were recruited, subject to no previous sleep disorders, among other criteria. Each participant was required to partake in two conditions, namely a day condition (09h00–11h00) and a night condition (23h00– 01h00). Each condition consisted of a 90 minute dual task; the primary task was a tracking task, in which participants were instructed to track a white line as accurately as possible. A secondary peripheral response task was introduced, in which participants were instructed to respond as quickly as possible to the peripheral stimuli, by pressing one of two clickers located on the steering wheel. The peripheral stimuli were located at 20º, 30º and 40º visual angle. Psychophysiological, performance and subjective measures were obtained before, during and after the main task. The pre- and post-tests included core body temperature, critical flicker fusion frequency threshold, a digit span memory test, Wits Sleepiness Scale and a NASA-TLX questionnaire. The psychophysiological and performance measures of heart rate, heart rate variability, blink frequency, blink duration, lane deviation, number of saccades towards peripheral stimuli, response time to peripheral stimuli and the percentage of missed peripheral responses were all recorded throughout the 90 minute main dual task. The results revealed significant differences (p<0.05) for heart rate variability, number of saccades towards peripheral stimuli and the Wits Sleepiness Scale, with regard to time of day. For time on task, significant effects were established for lane deviation, response time to peripheral stimuli, percentage of missed peripheral responses, heart rate, heart rate variability, blink frequency, blink duration, critical flicker fusion frequency threshold, core body temperature and the Wits Sleepiness Scale. Eccentricity was analysed and found to be significant for response time to peripheral stimuli, as well as for the percentage of missed peripheral responses; there was a significant increase in both measures with an increase in the stimuli eccentricity. No significances were established for time of day or between the pre- and post-tests conducted for the digit span memory performance; however, a significant interactional effect between the two was established. When assessing the percentage rate of decrement of driving performance compared to the percentage rate in the decrement of the missed peripheral responses, it was found that the percentage rate of decrement was equal for both measures. Thus from this research it can be seen that, concurrent with a decrement in driving performance, there are adverse effects on an individuals' peripheral vision, which have great implications for the safety of workers in industry and transport, as well as motorists. It was also established that time on task is possibly a more appropriate variable to consider than time of day, when implementing work schedules and rest breaks in industry, transport and fields alike, as more significant findings were seen for time on task compared to time of day. , Adobe Acrobat 9.53 Paper Capture Plug-in
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The analysis of the strain level and the predicted human error probability for critical hospital tasks
- Authors: Burford, Eva-Maria
- Date: 2012
- Subjects: Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5104 , http://hdl.handle.net/10962/d1005182 , Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Description: South African hospitals, as a result of numerous factors, have the problem of an increasing workload for nursing staff, which in turn may affect patient treatment quality. This project aimed at addressing patient treatment quality specifically from the perspective of worker capabilities by investigating the strain level and predicted human error probability associated with specific patient-centered tasks in the South African health care sector. This was achieved through two independent yet interlinked studies which focused on seven patient-centred tasks. The tasks analysed were the tasks of setting up and changing intravenous medication, administering injection and pill medication, measuring blood glucose, temperature and heart rate and blood pressure. In the first study, work environment and task characteristics, task structure and execution were analysed. In addition to the task execution, the resulting strain levels, in the form of heart rate measures and subjective ratings of workload, were studied. The second study determined the error protocols and predictive error probability within the healthcare environment for the seven pre-defined tasks. The results for the first study established that different organizational and environment factors could affect task complexity and workload. The individual task components and information processing requirements for each task was also established. For the strain analysis, significant results for the tasks were determined for heart rate frequency and the heart rate variability measures, but some of these were contradictory. For the second study, specific error protocols and error reporting data were determined for the hospital where this research was conducted. Additionally the predictive error probability for the pre-defined tasks was determined. This combined approach and collective results indicate that strain and predictive error probability as a result of task workload can be determined in the field as well as being able to identify which factors have an effect on task strain and error probability. The value of this research lies in the foundation that the gathered information provides and the numerous potential applications of this data. These applications include providing recommendations aimed at improving nursing work environment with regards to workload, improving patient treatment as a result of a reduction in errors and the potential foundation these results provide for future research
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- Authors: Burford, Eva-Maria
- Date: 2012
- Subjects: Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5104 , http://hdl.handle.net/10962/d1005182 , Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Description: South African hospitals, as a result of numerous factors, have the problem of an increasing workload for nursing staff, which in turn may affect patient treatment quality. This project aimed at addressing patient treatment quality specifically from the perspective of worker capabilities by investigating the strain level and predicted human error probability associated with specific patient-centered tasks in the South African health care sector. This was achieved through two independent yet interlinked studies which focused on seven patient-centred tasks. The tasks analysed were the tasks of setting up and changing intravenous medication, administering injection and pill medication, measuring blood glucose, temperature and heart rate and blood pressure. In the first study, work environment and task characteristics, task structure and execution were analysed. In addition to the task execution, the resulting strain levels, in the form of heart rate measures and subjective ratings of workload, were studied. The second study determined the error protocols and predictive error probability within the healthcare environment for the seven pre-defined tasks. The results for the first study established that different organizational and environment factors could affect task complexity and workload. The individual task components and information processing requirements for each task was also established. For the strain analysis, significant results for the tasks were determined for heart rate frequency and the heart rate variability measures, but some of these were contradictory. For the second study, specific error protocols and error reporting data were determined for the hospital where this research was conducted. Additionally the predictive error probability for the pre-defined tasks was determined. This combined approach and collective results indicate that strain and predictive error probability as a result of task workload can be determined in the field as well as being able to identify which factors have an effect on task strain and error probability. The value of this research lies in the foundation that the gathered information provides and the numerous potential applications of this data. These applications include providing recommendations aimed at improving nursing work environment with regards to workload, improving patient treatment as a result of a reduction in errors and the potential foundation these results provide for future research
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The effects of sustained attention, workload and task-related fatigue on physiological measures and performance during a tracking task
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
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- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
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