Strength and conditioning of adolescent male cricket players
- Authors: Pote, Lee
- Date: 2018
- Subjects: Cricket South Africa , Cricket injuries South Africa , Cricket Physiological aspects , Cricket Coaching South Africa , Physical fitness for youth South Africa , CricFit
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63933 , vital:28508
- Description: Background: Modern day cricketers are faced with longer, more strenuous seasons which are more physically demanding than the traditional forms of the game. Due to these increased physical demands, players are more prone to both overuse injuries, particularly of the lower back (bowlers) and lower limbs (batsmen), as well as acute, impact injuries (fielders/wicket keepers). The increase in injury risk is of particular concern at younger levels as research has shown that adolescents are at a higher risk for injury than their adult counterparts. Therefore, there is a need for strength and conditioning programs that reduce the risk of injury and improve performance at this level. However, of the programs that are available, most are not multi-factorial in nature and are aimed at elite cricketers. This is of concern in low-to-middle income countries such as South Africa, where players often do not have access to facilities or equipment and thus need to be exposed to low-cost, no-cost training programs. Furthermore, most information is anecdotal and there is a distinct lack of injury prevention programs at an adolescent level. Objective: The purpose of this thesis was to investigate the strength and conditioning practices of adolescent cricket players, particularly from a South African context, where there is a distinct lack of resources. This was through the completion of three phases; firstly, a literature review was completed to determine the information currently available on injury prevention strategies in cricket. The review also examined the injury statistics of five major playing cricket nations. Secondly, a survey was conducted to determine the current strength and conditioning practices of schoolboy and university coaches in South Africa. Lastly, a novel intervention program (CricFit) was designed and implemented within an adolescent population. The main purpose of the intervention was to determine whether players’ physical fitness parameters improved over time and whether the risk of injury was reduced. Methods: For phase one of the thesis (review paper), a search of the different scientific databases was undertaken to determine the nature and incidence of injuries in cricket activity as well as well as current strength and conditioning practices in place to reduce these injuries. These injury statistics and prevention programs where then reviewed. For the survey based research, an online questionnaire, adapted from previous strength and conditioning studies, was sent to 38 school boy and 12 university teams that participated in the top competitions in South Africa. In addition to the previous questionnaires, cricket specific practices and injury statistic questions were added to the survey. The survey consisted of three sections: a general, cricket specific and injury and injury prevention section. The survey also allowed coaches at both university and school levels to describe their practices and ideas in order to understand their basic knowledge of scientifically-based principles of strength and conditioning. Thus coaches were encouraged to explain what conditioning practices they implemented through a number of open ended questions which were then analysed for minor and major themes. The focus of the intervention program was to improve general physical fitness for cricket players. The study was a pre- and post-test design where twenty eight schoolboy cricketers (aged 15-19 years) were allocated to a control (n=14) or experimental (n=14) group during the cricket pre-season period. Both groups performed traditional net and field based training over a four week period (one net and one field based session), with the experimental group performing an additional two, 35-45 minute, conditioning sessions per week (“CricFit” intervention program). The intervention consisted of exercises that centred on the movement demands associated with the sport of cricket as well as injury prevention exercises (specifically Nordic lowers and core strength). Prior to and post the four week intervention period, responses were measured using a test battery that was designed to replicate the demands of cricket activity. Results: The results indicate on overall thesis summary. The literature view showed that there is a limited amount of injury prevention programs available for adolescent cricket players. It was also confirmed that for both adolescent and adult players, fast bowlers (lower back), followed by batsmen (lower limbs) and then fielders (impact) are the most prone to injuries. The survey showed that schools and universities in South Africa do conduct some form of conditioning, workload monitoring and injury prevention exercises; however the incorrect practices are being administered when considering the movement demands and most common injuries in cricket. It was also shown that most coaches did not have the adequate qualifications and experience to implement acceptable strength and conditioning programs. For the intervention study, both the control and experimental groups showed significant (p<0.05) improvements in most responses, but the changes for the experimental group were greater than those shown in the control group. Furthermore, significant (p<0.05) changes were shown between the two groups (control vs. experimental) for percentage body fat (12 vs. 11%), sit and reach flexibility (40.79 vs. 80.50mm), plank time (105.36 vs. 185.29s), 20 m sprint time (3.27 vs. 2.84s), push ups (34 vs. 41) and 25 m shuttle distance (699.18 vs. 746.79m). Conclusion: Coaches need to be educated and trained to implement the correct strength and conditioning practices at an adolescent level as well as to better understand the link between the movement demands and principles of testing and training. An improved education process may be needed to improve the quality as well as the qualifications of strength and conditioning coaches. If coaches and trainers are educated properly, then the “CricFit” intervention program may be used to improve cricket specific fitness throughout the pre-season period. The “CricFit” programme is useful in countries such as South Africa, where often players do not have access to coaches and facilities and thus can be implemented easily with minimal cost.
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Strength and conditioning practices of high school rugby coaches: a South African context
- Authors: Robinson, Bradley Charles
- Date: 2018
- Subjects: Rugby football coaches South Africa , Rugby football Coaching , Rugby football Physiological aspects , Rugby football Training , High school students Social conditions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63459 , vital:28413
- Description: Although the sport of rugby union is well established, the strength and conditioning practices of high school level players are not well known. Therefore, the purpose of this study was to examine the current strength and conditioning practices that coaches implement at South African high school level rugby. A secondary purpose was to compare practices between different types of schooling systems available in South Africa. An online survey or in person interview (depending on the school), adapted from previous strength and conditioning questionnaires, was conducted with 43 responses; including 28 schools among the top 100 rugby schools in South Africa for 2016 and 15 no-fee paying public schools in the Eastern Cape Province of South Africa. Results indicated that the top 100 rugby schools implement conditioning practices similar to the best-known international practices compared to no-fee paying schools who lacked the knowledge and skills in various strength and conditioning principles. It was found that all no-fee paying school coaches had insufficient qualifications to administer the correct training techniques. Coaches at all schools lacked the appropriate knowledge on injury prevention and scientifically based training programmes. It was concluded that education and skills around the best strength and conditioning practices for school level coaches needs to be improved and particularly in less privileged schools. The main goal being to reduce the risk of injury and improve performance across all sectors of the rugby playing population within the country. This was deemed crucial to the transformation goals set out by the South African Rugby Union, which would benefit from player development in lower socioeconomic schools.
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The effects of intermittent task parameters on muscle fatigue development during submaximal dynamic exertions
- Authors: King, Josephine Claire
- Date: 2018
- Subjects: Muscles -- Physiology , Muscles -- Wounds and injuries , Fatigue , Human engineering , Occupational diseases
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63855 , vital:28498
- Description: The negative effects of localised muscle fatigue on accidents, injuries and poor work performance are well known, as is the realisation that modifying task characteristics can minimise fatigue development. A large amount of literature has investigated the effects of task-dependent factors on localised muscle fatigue, most studies have focussed on prolonged or intermittent static (isometric) exertions. Few studies have investigated muscle fatigue development during more complex tasks, namely those which resemble common work activities and which tend to be intermittent and dynamic in nature. More specifically, the interactions between the main intermittent parameters - duty cycle, force level, and cycle time - during dynamic exertions are poorly understood. The purpose of this study was to investigate the effects of cycle time and combinations of duty cycles and force levels on the development of muscle fatigue during submaximal dynamic exertions while the overall mean muscle load was kept constant. A two-factorial repeated-measures experiment was developed for this study. Nine experimental conditions, each lasting 16 minutes, aimed at inducing muscle fatigue in the middle deltoid muscle via intermittent dynamic shoulder abduction and adduction motions at three cycle times (30, 60, and 120 seconds) and three combinations of duty cycles and force levels. The percentage of muscle activation during one cycle (i.e. the duty cycle) varied depending on the exertion intensity (force level) so that the overall mean muscle load remained consistent throughout all experimental conditions, namely at 20% of maximum force exertion. As a result, the three duty cycle/force level combinations were: 0.8/25% of maximum voluntary force (MVF), 0.5/40%MVF, and 0.4/50%MVF. Muscle fatigue development was inferred by changes in peak torque, total work, average power, local Ratings of Perceived Exertion (RPE), and surface electromyographical (EMG) activity (time domain and frequency domain).Two-factorial analyses of variance with Tukey post-hoc tests were used to identify significant condition effects at p<0.05. All dependent measures showed that muscle fatigue was induced by the 16-minute fatigue protocol. Peak torque, total work, average power, and EMG percentage of maximum showed that cycle time and the duty cycle/force level combination had no effect on the development of muscle fatigue, whereas the measures evaluated during the 16-minute fatigue protocol did. The cycle time of 120 seconds induced the greatest change in six of the eight variables, while the duty cycle/force level combination (0.8/25%) also resulted in the greatest effect in six of the measures. Fatigue was also found to be dependent on the interaction of cycle time and duty cycle/force level combination. The conclusion draws from this study is that shorter cycles and activities with short activation periods, and proportionally longer rest breaks result in the lowest fatigue developments.
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A holistic investigation of amateur batters performance responses to a century protocol: a focused cognitive perspective
- Authors: Goble, David
- Date: 2017
- Subjects: Cricket -- Batting -- Physiological aspects , Cricket players -- Physiology , Cricket players -- Health and hygiene , Cognition -- Testing , Neurophysiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/40725 , vital:25020
- Description: No cognitive study has implemented an exercise modality that requires both physical effort and cognitive control, therefore, the effects of such exercise are unknown. Additionally, no studies have investigated how prolonged batting impacts cognitive functioning nor how physical responses and cognitive functioning are related while batting. At intensities of 6070 percent heart rate maximum, acute and prolonged bouts of physical activity have been shown to improve cognitive functioning. At higher intensities, the beneficial effects are minimal and in some cases performance is impaired. Therefore, the aim of this investigation was to determine how prolonged intermittent batting (a task that requires high muscular and cardiovascular loads but also continuous cognitive control) affects cognitive, physiological, physical and biophysical responses in amateur batters. Further aims included to test the reliability of the method employed in assessing these responses. To answer this question, the investigation was separated into three studies: phase 1 (a large-scale pilot) and phase 2 and 3 (a repeated measures test-retest hypothesis). In each phase, batters completed the 30 over BATEX simulation, which replicated the demands of scoring a one-day international century. To establish physiological, physical and perceptual strain; heart rate, sprint times and perceived exertion data were collected each over. Changes in body mass over time were compared to determine the effects of fluid loss on cognitive performance. Before, during and after the simulation, psychomotor function, visual attention, working memory, visual learning and memory as well as executive functions were assessed (CogState brief test battery). During cognitive assessments, heart rate and heart rate variability parameters were sampled so that autonomic modulation of the heart could be determined. The methodological differences between phase 1 and phase 2 and 3, were (respectively); the frequency of cognitive assessments (five vs. three), the samples used (15 schoolboy vs. 16 academy batters), hydration protocols (250ml of Energade vs. water ad libitum) and a singular change in a physical dependent variable (batting accuracy vs. vertical jump). In schoolboy and academy batters, the prolonged batting simulation placed significant strain on the cardiovascular and muscular subsystems; increasing heart rate (p<0.01), decreasing body mass (p<0.01) and deteriorating sprint performance (p<0.01) over time. In each sample, batters’ perceived exertion increased significantly (p<0.01) and exertion was highest in the final over of the protocol. Interestingly, the changes in cardiovascular and muscular responses were larger in schoolboy batters. While the cognitive performance decrements over time were not significant in academy batters (p>0.05; d<0.2), the magnitude of impairment in psychomotor function (p>0.05; d = 0.37), visual attention (p>0.05; d = 0.56), working memory (p>0.05; d = 0.61) and executive function (p>0.05; d = 0.58) was larger in schoolboy batters. In both samples, the simulation altered the modulation of heart rate significantly. Heart rate variability decreased linearly with time spent batting (p<0.01; d>0.8). During cognitive assessments, heart rate variability increased with time-on-task, where responses were significantly higher (p<0.05) in the last task of the battery compared to the first. Importantly, the results of the retest phase were the same as in the test phase and only two condition effects were observed; (i) heart rate (retest lower: p<0.04;d = 0.39), (ii) body mass (retest lower: p<0.03;d = 0.09). A task-related condition effect in heart rate variability (PNN30) was also observed (retest higher: p<0.03; d = not calculated). Resultantly, the test-retest reliability of phase 2 and 3 was high. The results indicate that prolonged intermittent batting at an intensity of 64-77 %HRmax impaired cognitive functioning in amateur batters. However, the cardiovascular and muscular strain induced by prolonged intermittent batting and its effects on cognitive functioning are mediated by intrinsic and extrinsic factors (age, training status, playing experience and hydration). Therefore, while prolonged batting has similar effects on cognitive functioning as acute bouts of physical activity, they do not share the same relationship. The author hypothesises that the continuous cognitive component inherent in prolonged batting mitigates the beneficial effects of physical activity, as demonstrated previously. Future research is needed to elucidate this relationship. Additionally, player experience affects the way in which batters regulate performance while batting; which also affects the rate of and magnitude of impairment during batting. Finally, the methodological limitations of this study provide direction for future research into batting.
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Appropriate integration of workers with physical limitations into a manual workplace – development of an assessment tool
- Authors: Pearson, Jessie T
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8209 , vital:21368
- Description: Background: People with physical limitations can contribute significantly to society and the economy, however, barriers to full and effective participation in the labour market often hinder decent employment. In light of this, placement decisions of impaired workers should be based on detailed information of the nature of the jobs available, as well as individual capabilities of the worker. An ergonomics approach to design attempts to achieve an appropriate balance between the capabilities of the worker and the requirements of the task and uses this balance to improve productivity and encourage physical and mental well-being, job satisfaction and safety. A specific analysis tool which can be applied to various workplaces and jobs, and provide information for decisions regarding placement of physically limited workers, will help to increase the percentage of correct placement in an appropriate workplace, resulting in optimum productivity and worker safety. Methods: An assessment tool which allows matching of job requirements and worker capabilities was developed based on a theoretical framework from Mattison and Goebel (2007), as well as principles defined by Almgren and Schaurig (2012) and Demura and Nakada (2010). The tool assesses range of motion, force and time components of the physical requirements of different tasks involved in the job, as well as movement capabilities and limitations of the worker. The tool was pilot tested in a case study with an above the knee amputee working at a research facility. Results: The tool successfully provided information regarding the matching of the work to the identified job. The output of the tool highlighted two tasks which would place the worker at risk due to physical requirements of the tasks being greater than movement capabilities of the worker. These tasks need to be further investigated to determine if accommodations can be made to assist the worker in safely performing the task, or if the job is not suitable for the worker. Conclusions: The tool developed was useful in providing information to inform appropriate placement of the physically limited worker. Further research needs to be done to validate and determine reliability of the tool.
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Assessing the physical fitness level of children with intellectual disability in the Grahamstown region of the Eastern Cape, and subsequently designing, implementing and evaluating the efficacy of an exercise intervention
- Authors: Parsons, Samantha Lee
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19723 , vital:22478
- Description: Background: Extensive research has addressed physical fitness as an agent in promoting health and well-being; however, there is little research on this topic for special populations, such as individuals with intellectual disability and even less relating to the South African context. Children with intellectual disability attending special need schools in disadvantaged communities in the Eastern Cape have lacked the opportunity to participate in structured physical education programs. Implementing a solution to this problem was seen to be a challenge, due to the lack of informative research and available data. Aims: The purpose of this research was two-fold; firstly, it aimed to identify the physical fitness levels of the intellectually disabled children in the Grahamstown region of the Eastern Cape province of South Africa; and secondly, it aimed to implement and evaluate the efficacy of an exercise intervention programme on physical fitness in a local school for children with intellectual disability. Phase 1: The descriptive study compared basic anthropometric as well as physical fitness measures from a sample of participants with intellectual disability (n=29) with a comparable sample of typically developed children (n=25). There were 15 males and 14 females in the intellectually disabled sample group, with an average age of 10.69 ± 1.26 years, and the typically developed sample had 13 males and 12 females, with an average age of 10.51 ± 0.74 years. The anthropometric measures included stature and mass; while the health-related physical fitness components included cardiorespiratory endurance, muscular endurance, strength, body composition, and flexibility; and the skill-related physical fitness components were balance, agility, speed, power, coordination and reaction time. The results revealed that the children with intellectual disability were significantly shorter in stature and lighter in mass (p <0.001) compared to their typically developed peers. Muscular endurance and strength, balance, speed, power, coordination and reaction time were poorer among those with intellectual disabilities (p <0.05). Cardiorespiratory endurance, flexibility and agility were similar between groups. Results of the correlation analyses determined significant (p <0.05) relationships between certain health-related and/or skill-related physical fitness components, which were instrumental for selecting measures for Phase 2. The physical fitness components that had the most significant (p <0.05) correlations were speed with five significant correlations, both muscular endurance and balance with six, coordination with seven, and power with eight significant correlations of the eleven physical fitness components. The comparative results, in conjunction with the correlations, determined that the most suitable physical fitness components to be implemented in the exercise intervention for Phase 2 were muscular endurance, balance, and power. Phase 2: The intervention study was a case-control study (intervention group: n = 16; control group: n = 15), whereby the intervention group was exposed to an 8-week multi-modal exercise intervention training muscular endurance, balance and power. Pre-and post-intervention measures were performed using the same eleven physical fitness tests as in Phase 1. The interaction effects and effect sizes were determined and the results showed significant improvements and large effect sizes for the intervention group’s performance of muscular endurance (p=0.026; d=0.617) and power (p<0.000; d=0.999), whereas no significant changes were found for balance. Furthermore, the exercise intervention also impacted the overall level of physical fitness, as significant changes were found for cardiorespiratory endurance (p<0.001; d=0.98), strength (p=0.021; d=0.654) and flexibility (p=0.032; d=586). In conclusion, the exercise intervention was effective for improving the intellectually disabled participants’ muscular endurance and power but not found effective for balance.
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Cardiovascular disease risk in Black and Caucasian females: an Eastern Cape sample
- Authors: Remsing, Sandra Claudia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/40737 , vital:25021
- Description: The purpose of this study was to investigate cardiovascular disease risk in Black and Caucasian urban working females of the Makana region of the Eastern Cape. One- hundred and sixty six age-matched urban-working individuals (Black n = 88; Caucasian n = 78) voluntarily participated in this cross-sectional study. Cardiovascular disease risk was assessed in four categories: 1) obesity, classified as ‘morphological risk’, 2) blood pressure, classified as ‘cardiovascular risk’, 3) diet, physical activity, smoking, and alcohol consumption, classified as ‘lifestyle risk’, and 4) education and income, classified as ‘socioeconomic factors’. Results showed that Black females were significantly (p<0.01) heavier than Caucasian females and categorized as ‘obese’ according to BMI classifications (31.19 ± 8.09 kg.m2 and 25.90 ±4.67 kg.m2, respectively). Black females also presented with significantly (p<0.01) higher waist circumferences and waist-to-stature ratios, further confirming the obesity prevalence in this group. When accounting for those who were on anti-hypertensive mediation, Black females additionally presented with significantly (p<0.05) higher blood pressure, categorizing them as ‘pre-hypertensive’ (MAP = 98 ± 16 mmHg and 85 ± 11 mmHg, respectively). These results therefore placed Black females at increased cardiovascular disease risk compared to Caucasian females. With respect to lifestyle factors, Black females consumed significantly (p<0.05) more kilojoules carbohydrates, and total sugar than Caucasian females, and expended more physical activity MET- minutes per week (2688.86 ± 1486.56 MET-minutes and 1828.27 ± 2238.10 MET- minutes, respectively). However, reduced validity of physical activity data as well as poor dietary recall limited the interpretations of these findings. In addition, despite significant differences between smoking and alcohol consumption between groups, the majority of both Black and Caucasian females reported being non-smokers and consumed alcohol minimally. Thus, these were concluded to be unlikely contributors to cardiovascular disease risk in these samples. Socioeconomic results nevertheless expectedly showed that Black females were significantly (p<0.05) less educated, and subsequently earned lower incomes. It was thus concluded that this may be a likely contributor to higher cardiovascular risk in Black females. Future recommendations include the incorporation of exercise intensity measures as well as objective measures of habitual diet. This is in order to get a clearer understanding of the impact of these lifestyle factors on cardiovascular disease risk.
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The effect of different seating conditions, in aircrafts, on passenger comfort and the use of cabin space
- Authors: Olley, Emma-Jane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19734 , vital:22479
- Description: Although aircraft cabin design has improved over the years, passengers continue to complain about sitting discomfort whilst flying. These complaints are often centred on the cramped and restricted seating conditions. Whilst passenger comfort is important, in order for airline companies to attract and retain customers, it is also important to design for cabin space needs. Denel Aviation intends to build a South African Regional Aircraft (SARA) that will fly point-to-point, linking regional centres and intends to design aircraft seats that not only optimise passenger comfort, but which also save cabin space. The aim of this investigation was two-fold. The first aim was to determine how aircraft backrest angle affected passenger comfort, ease of seat access, perceived restriction and legroom, with different seat pan angles and seat heights. The second aim was to determine whether passenger comfort was affected with the most preferred backrest angle for each seat pan angle and seat height. Determining how seat pan angle and seat height affect the preferred angle of the backrest was considered important as Denel intend to use aircraft seats with a non-adjustable backrest angle. For this study, 80 participants were recruited from Rhodes University and the general Grahamstown population. The participants consisted of 40 males and 40 females and were not limited by race, ethnicity or culture. The participants were classified into two age groups; 18-30 years of age and 31-60 years of age. Participant stature, body mass, BMI and lower leg length was recorded to determine the effect these factors had on sitting comfort when the participants were seated in different seating conditions. From the results obtained, it was found that, by altering seat height, seat pan angle, and backrest angle, passenger comfort can be optimised. Furthermore, it was found that certain combinations of seat height, seat pan angle and backrest angle are more beneficial with regards to saving aircraft cabin space. However, this means that a compromise needs to be found for SARA as passenger comfort needs to be optimised, whilst decreasing the use of cabin space to reduce costs.
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The effect of submersion in water and breathing modality (assisted breathing and apnea) on different stages of the information processing chain
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
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The effect of total standing duration during sit-stand regimes on cognitive performance, rating of perceived exertion and heart rate frequency
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
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The effects of the type of rest breaks on return-to-task performance in semi-automated tasks with varying complexities
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
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A comparison of muscle fatigue responses between static and quasi-static exertions
- Authors: Nel, Conrad
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3475 , vital:20502
- Description: Background: This study examined localized muscle fatigue responses from sub-maximal quasi-static work protocols and additionally how it compares to purely static work. The goal was to produce research that enhances the understanding of the demands on muscles during manual work to aid in preventing injuries stemming from localized muscle fatigue. Injury rates remain a problem in manual labour sectors, particularly for the lower back and shoulder regions for the manufacturing, service and construction sectors, and for knee and elbow flexors in the sports sector. Few studies have looked at quasi-static work and what the resulting fatigue characteristics are, especially when compared to purely static or purely dynamic work. This comparison is particularly important due to the fact that risk assessment tools that are currently utilized to assess risk in the working environment are based on fatigue studies that focus on purely static or purely dynamic work. This requires attention as many working situations are neither static nor dynamic, but rather quasi-static in nature, with aspects of both dynamic and static muscle components. The scope of this study only encompasses the comparison between purely static and quasi-static work. Objectives: This study had two objectives, firstly, to determine what the fatigue characteristics of quasi-static work are and how it compares to fully static work. Secondly, to determine whether an underlying static component within an otherwise dynamic muscle force affects localized muscle fatigue compared to quasi-static work that has equal amounts of effort but with no underlying static component. Methods: Four experimental conditions were tested, each on four muscles, namely the medial deltoid, bicep brachii, bicep femoris and erector spinae muscles. To test the two objectives of this study, 16 volunteers performed a five minute fatigue protocol, that either entailed a fully static condition which involved: 1) producing a steady force at 25 percent of maximum voluntary force, 2) a quasi-static condition with fully dynamic muscle force that alternates the required force level between zero and 50 percent of maximum force, 3) a quasi-static condition with an underlying static component of five percent of maximum force, or 4) a quasi-static condition with a large underlying static component of 15 percent of maximum force. All the experimental conditions in this study had the same average workload of 25 percent of maximum voluntary force over time and thus total workload. The dependant variables of interest were ratings of perceived exertion, changes in muscle fibre recruitment (% of maximum EMG activity), maximum force and center frequency from a spectral analysis of the surface electromyography. These were measured throughout the protocols at one minute intervals to determine how muscle fatigue progressed, and how the fatigue responses differed between conditions. Results: The data from comparing fully static and quasi-static work showed that of the variables measured, the rating of perceived exertion (RPE) and maximum force data indicated that for bicep brachii and bicep femoris muscles, fully static work is more fatiguing than work that alternates between zero and 50 percent of maximum force. The results for the medial deltoid and erector spinae muscles were inconclusive. The findings regarding the comparison between quasi-static conditions with and without an underlying static component revealed that an underlying static component results in greater fatigue when compared to a quasi-static condition with no static component. The results may also suggest that a larger static component coupled with a smaller peak force results in less fatigue than a condition with a small underlying static component coupled with a higher peak force in some scenarios, provided total work is kept constant. All conditions had to have the same workload in order to be validly compared and thus the condition with a larger underlying static component had a lower peak force compared to the condition with no underlying static component or the condition with a small underlying static component. Conclusions: This study presented evidence that quasi-static work does not induce fatigue when measured by RPE and drop in maximum force in the same way as static work. Additionally, the results indicate that a larger underlying static component does not necessarily fatigue a muscle faster if the overall workload is kept constant. However, the results do suggest that any underlying static component will increase the demand on a muscle when compared to a muscle exertion with no static component. When considering the available literature on how muscles fatigue during low level static contractions, the current understanding is that the larger the force during a static contraction, the faster the onset of fatigue and decrements in performance occur. The results of this study suggest that this same relationship cannot be applied to quasi-static work where an underlying static component is part of an otherwise dynamic muscle force. Thus total workload or peak force may play a larger role than the static muscle exertion in some scenarios.
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An insight into the profile characteristics and technical batting skill of adolescent cricket players
- Authors: Clark, Matthew Edward
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2838 , vital:20331
- Description: Background: Current traditional cricket practices incorporate the use of a netted-off pitch to provide cricket players the opportunity to hone their skills with bat and ball. The lack of ecological validity of these training environments results in the absence of important task and environmental constraints which influences the manner in which the sport is played. Objectives: The purpose of the current research was two-fold: firstly, it aimed to establish a profile database of adolescent cricket players in the Eastern Cape province of South Africa; and secondly, it aimed to investigate the efficacy of a constraints-led training intervention on skill development in adolescent cricket batsmen. Methods: Study I required 90 participants (u13: n = 40; u15: n = 50) to perform measures pertaining to anthropometric, morphological, flexibility and physical performance characteristics. This included stature, mass, body composition, limb length, flexibility, agility, and power measures. Study II was a case-control study (u15: n = 24), whereby the experimental group (n = 12) was exposed to a constraints-led batting protocol during the course of the cricket season. The objective of the protocol was to encourage the manipulation of the ball around the playing field. Pre- and post-intervention measures were performed using a batting skills test, which assessed batsmen’s capability to manipulate the ball to various areas of the playing field. Results: Study I revealed significant differences (p <0.0001) in stature, mass, limb length and power variables when comparing the u15 age group with the u13 age group. No differences were recorded for agility. The u13 age group had greater linear correlations for the variables of interest compared to the u15 age group. Study II revealed no differences in technical skill between the experimental group and the control (p <0.315).. The tests also revealed that adolescent batsmen favoured hitting deliveries through the extra-cover scoring zone. The third-man and fine-leg scoring zones were least preferred to hit deliveries through. A number of limitations to the study design resulted in the inability to determine the efficacy of a constraints-led batting protocol on skill development in an adolescent batting cohort. Conclusion: The results of study I indicated that the onset of puberty played an important role in the measures and performances between the u13 and u15 age groups. The results of study II indicated that adolescent batsmen are not adept at manipulating the ball around the field. Recommendations are provided for both studies.
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An investigation into the interaction effects of simultaneous physical and cognitive task execution on performance, perceptual and physical responses
- Authors: Ross, Natalie
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3562 , vital:20525
- Description: Many modern day work environments require some degree of dual tasking, particularly the simultaneous performance of cognitive jobs alongside physical activity. The nature of such tasks is often job dependent and may require cognitive functions such as perception, decision making, memory, or response selection/execution in conjunction to task specific physical requirements. Previous research has indicated a possible relationship between concurrent physical and cognitive demands and task performance, safety and efficiency. However, this research is limited and inconsistent. The current study aimed to identify the interaction, if any, between concurrent physical and mental demands, and determine the impact of sensory modality and stage of information processing on this interaction, with specific focus on the performance, perceptual and physical responses during different types of cognitive tasks performed concurrently with a lifting task. 20 (10 male, 10 female) Rhodes University students participated in this study. Each participant performed 9 test conditions - a physical lifting task, a visual and an auditory memory task, and a visual and an auditory decision making task in isolation, as well as the lifting task concurrently with each of these cognitive tasks. Performance was recorded via accuracy and work output of cognitive tasks and the number of lifts for each condition. Perceptual measures were obtained via the Borg RPE and Subjective Workload Assessment Technique. Spinal kinematics were measured using the Lumbar Motion Monitor, while muscle activity of the Erector Spinae, Rectus Abdominis, Rectus Femoris and Biceps Femoris muscles were recorded using the Biometrix Data Logger surface EMG equipment. Mean results were analysed using a dependent T-test to observe any general interaction, and a Two-way ANOVA for the impact of sensory modality and stage of processing. Individual responses were also considered to gain better understanding of both intra and inter-human variability under the various test conditions. Results showed a significant decrease in cognitive performance, increased perception of physical effort, time pressure, mental effort and psychological stress under simultaneous physical and mental demands, while no significant differences in physical responses were observed. Further observations included increased dual-task interference during visual and decision-making tasks when combined with physical demands compared to that of auditory and memory tasks respectively. Individual responses showed large variability between individuals indicating the presence of positive, negative and non-responders to concurrent physical and mental demands. Results therefore imply an individual specific interaction between concurrent physical and mental demands that may or may not be detrimental to worker productivity, job error, injury rates and worker well-being, and that the type of cognitive task performed may impact this interaction.
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Do differences in personality traits affect how drivers experience music at different intensities?
- Authors: Tlhoaele, Kebaabetswe
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3695 , vital:20536
- Description: Various researchers have investigated contributing factors towards the number of acute traffic incidences in and around Southern Africa. Some of these contributing factors include: the skills component of the driver predominately attributed to driving experience as well as the behavioural component influenced by the driver’s natural predisposition, individual differences and personality traits. In order to manage these factors drivers have developed varying coping mechanisms. One of these coping mechanisms is listening to music while driving, which is readily available in most cars and extensively used predominately during long duration driving. Listening to music neither increases one’s driving duration (as opposed to taking several breaks), nor does it interfere with the physical movements of driving (in the manner that eating and drinking may), but it might impact the concentration and attention of some drivers. This is based on the notion that music is assumed to impact arousal and cognitive ability. While there are several studies on the effect of music on driving performance and personality traits very few studies have looked at whether music has a positive or negative effect on driving performance based on differences in personality traits; and whether the extent of this effect might differ for different intensities of music? Consequently, this study aims to understand and determine the extent to which different personality traits predict the effect that listening to different music intensities has on driving performance. The impact of differing music conditions on the different personality traits used a repeated measures design and a between group design with respect to the personality traits with a sample size of (n=25)-16 females and 9 males-and their ages ranged between 19-35 years of age. The average age and standard deviation for this sample size was 22 years±2. A low-fidelity driving simulator task was utilised in order to provide a controllable, repeatable and a safe environment as compared to a real road situation. Personality was assessed using an online Big-Five Inventory scale (extraversion, agreeableness, conscientiousness, neuroticism, openness). All the different personality groups completed three conditions (45 minutes each) in a randomised order (without music, moderately loud music and loud music). Psychophysiological parameters i.e. heart rate frequency (HRF), heart rate variability (HRV) and eye movements (pupil diameter, eye speeds, fixation duration, blink frequency and blink duration) and driving performance were measured continuously. Subjective performance Multidimensional Driving Style Inventory was measured once-off prior to completion of the testing sessions, whilst the NASA-Task Load Index scale and Perceived control of participants were assessed after each condition. The expected outcomes revealed that music had an effect on objective driving performance (tracking deviation and reaction time) and psychophysiological measures only for participants of certain personality types while other personality types were unaffected by music. The subjective performance measures did not follow the same trend as objective performance measures. The conditions did not reveal an effect on driving performance, for most of the psychophysiological parameters and subjective measures. There was mainly a significant time on task effect and interactional effects on the psychophysiological measures (physiological and oculomotor) parameters at (p<0.05), but not on the subjective measures as anticipated. The study illustrated that the there are differences between personality traits. There was difficulty in the interpretation of the results based on the complexity of the findings for which each hypothesis was partially accepted. The research may establish practical implications for traffic safety campaigns in South Africa, as well as influence driving education for citizens. Assessing the personality trait would help to form an understanding as to which of the personality traits might be affected negatively from listening to music while driving and those that might benefit. Moreover, this study may assist motorists in understanding the implications of listening to music while driving as this may sometimes elicit risky driving behaviour and possibly cause an accident that may result in death.
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The effects of a gradual shift rotation and a split shift nap intervention on cognitive, physiological and subjective responses under simulated night shift settings
- Authors: Davy, Jonathan Patrick
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/517 , vital:19966
- Description: Introduction: Shift work, particularly work that occurs at night has been associated with numerous challenges to occupational safety and productivity. This stems from the associated extended wakefulness, circadian disruptions and sleep loss from the inversion of the sleep wake cycle, which predisposes shift workers to reduced alertness, increased fatigue and decrements in performance capacity. These effects may be exacerbated over consecutive night shifts as a result of reductions in sleep length associated with attempting to sleep against the alerting signals of the circadian rhythm during the day. Although a variety of shift work countermeasures exist, new and innovative fatigue management strategies are needed to mitigate the effects of night work. This study proposed two night shift interventions; the Rolling rotation and a split shift nap combination. Aims: The aim of this study was to explore the effects of these interventions to a conventional Fixed night shift arrangement. Selected performance, physiological and subjective measures were applied to track any effects during a five-day shift work study. Methods: The study was laboratory-based and performance was quantified through the application of computer-based perceptual, cognitive and motor tests. Student participants (24 females and 21 males) partook in the study, which adopted a nonrepeated measures design and spanned five consecutive days. During this time, participants were required to perform a simple beading task over five 8-hour shifts. Participants were split according to sex and chronotype between four independent conditions; 1. Fixed night condition required participants to complete one afternoon shift (14h00 – 22h00) and four consecutive night shifts (22h00 - 06h00) 2. Rolling rotation condition gradually “rolled” participants into the night shift by delaying the start and end of an afternoon shift by two hours each day (16h00 – 00h00, 18h00 – 02h00, 20h00 – 04h00, 22h00 – 06h00) until the times matched that of the Fixed night condition. 3. The split shift nap system was made up of two independent groups, both of which completed one afternoon (14h00 to 22h00) and four night shifts. The Nap early condition worked from 20h00 to 08h00, napping between 00h00 and 04h00, while the Nap late condition worked from 00h00 to 12h00 and napped between 04h00 and 08h00 during the night shifts. Napping, the opportunity for which was 200 minutes occurred in the laboratory, but post shift recovery sleep, for all conditions, happened outside the laboratory. During each shift, six test batteries were completed, in which the following measures were taken: 1. Performance: beading output, eye accommodation time, choice reaction time, visual vigilance, simple reaction time, processing speed and object recognition, working memory, motor response time and tracking performance. 2. Physiological: heart rate, heart rate variability (r-MSSD, normalised Low frequency power: LFnu). 3. Self-reported measures: subjective sleepiness and reported sleep length and quality while outside the laboratory. Results: Analyses revealed that: 1. Measures of beading performance, simple reaction time, vigilance and object recognition, working memory, motor response time and control, all physiological measures, except LFnu and subjective sleepiness demonstrated the effects of time of day / fatigue, irrespective of condition. 2. There was no evidence of cumulative fatigue over the four night shifts in the performance and subjective measures and most of the physiological indicators. Beading output decreased significantly over the course of the night shifts, while reported post shift sleep length was significantly reduced with the start of the night shifts, irrespective of condition. 3. The majority of the physiological and performance measures did not differ significantly between conditions. However, there were some effects: the Rolling rotation condition produced the highest beading output compared to the Nap late condition; working memory was significantly lower in the Nap late condition compared to the other conditions. Furthermore, the nap opportunity in both the Nap early and Nap late conditions reduced subjective sleepiness, while napping during the night shift reduced post shift sleep length compared to the Rolling rotation and Fixed night conditions. There was also evidence of sleep inertia following pre-post nap test comparisons, which mainly affected visual perception tasks in both nap conditions. Sleep inertia possibly also accounted for an apparent dissociation between subjective and performance measures. Conclusions: Quantifying and interpreting the effects of night shift work in a laboratory setting has limitations. These stem mainly from the limited ecological validity of the performance outcome measures adopted and the characteristics of the sample that is tested. However, in order to fully understand the efficacy of any shift work countermeasure, the laboratory setting offers a safe, controlled environment in which to do so. The conclusions should thus be considered in light of these limitations. Night shift work negatively affected all elements of human information processing. The combination of reduced physiological arousal, extended wakefulness, increased perceptions of sleepiness and reduced total sleep obtained explained these decrements in performance. While cumulative fatigue has been reported as a challenge associated with night shift work, there was no conclusive evidence of this in the current study. In the case of the Rolling rotation, the gradual introduction to the night shift delayed the inevitable reduction in alertness and performance, which limits the viability of this intervention. The inclusion of the nap interventions was associated with reduced perceptions of sleepiness, which did not translate into improved performance, relative to the Rolling rotation and Fixed night conditions. Apart from considerations of how to manage sleep inertia post nap, the split shift nap intervention can provide an alternative to conventional night shift work arrangements.
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The efficacy of a community based eccentric hamstring strengthening program in peri-urban Black South African soccer players
- Authors: Ryan, Bennett
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3573 , vital:20526
- Description: Introduction: Hamstring injury prevalence in soccer remains a major concern. Research in this context has focused on Caucasian populations with little attention given to other ethnic groups. The compatibility and applicability of such research to the South African context, particularly at an amateur level, may be minimal due to fundamental differences in physical characteristics, as well as complexities with regards to implementation. The aim of this investigation was therefore twofold. 1) Identify the lower extremity strength and performance profile of Peri-urban Amateur South African Players, and 2) Assess the efficacy of a community based intervention through the use of the Nordic Hamstring Exercise. Methods: 19 Black male Eastern Cape amateur players participated in a 12 week randomly controlled trial (9 = Control, 10 = Intervention). All participants completed regular training, while the intervention group, in addition, performed the Nordic Hamstring exercise post warm up. The incremental program design was taken from Mjolsnes et al. (2004), with a progressive increase in both sets and repetitions. Compliance was defined as completion of the required exercises for that session. Isokinetic strength evaluations (at 60°.s-1 and 180°.s-1) including assessment of peak torque and total work, as well as performance measures of countermovement and squat jump, were completed pre and post intervention, with the profile of the Peri-urban player the combined responses of both groups at baseline. Additionally, both the functional ratio (Eccentric Hamstrings/Concentric Quadriceps) and eccentric utilization ratio (Countermovement Jump/Squat Jump) were calculated. Results: Concentric quadriceps peak torque at baseline reported values of 195 (±22) Nm and 141 (±21) Nm at 60°.s-1 and 180°.s-1. Values of 162 (±21) Nm were observed for peak torque of the eccentric hamstrings at 60°.s-1, while 157 (±18) Nm was indicated at 180°.s-1. Mean functional ratio responses were observed as 0.83 (±0.11) and 1.12 (±0.16) for 60°.s-1 and 180°.s-1 respectively. Additionally, the eccentric utilization ratio responses were recorded as 1.04 (±0.08). Regarding the intervention, concentric quadriceps total work of the dominant limb significantly improved over the time course of experimentation within the intervention group. Other quadriceps variables, concentric hamstrings, squat jump capability and performance measures all reported no significant changes (p>0.05) over the course of assessment when compared to the control. Eccentric hamstrings peak torque observed significant improvements (p<0.05) of between 5.72 and 12.82 % within the intervention group, while the countermovement jump indicated a significant 15.59 % increase (p<0.05). Additionally, the functional ratio and the eccentric utilization ratio both indicated no significant changes (p>0.05), with a 2.48-7.66 % and 5.33 % improvement noted following completion of assessment. Conclusion: Isokinetic responses at baseline observed decreased quadriceps strength, and increased hamstring strength when compared to both amateur and professional populations examined in previous studies, for both isokinetic testing speeds. Additionally, performance measures indicated similar responses to other amateur populations. Regarding the intervention, significant improvements in eccentric hamstring peak torque and countermovement jump indicate the partial success of the present intervention. Additionally, while the functional ratio and eccentric utilization ratio reported no significant changes, improvements were noted within the intervention group while the control noted no change. The Nordic hamstring lower therefore resulted in strength improvements within the eccentric hamstrings, reported as a significant factor for injury risk, however, such changes were not sufficient to significantly impact the functional ratio. It can be concluded that community based programs within South Africa have the potential to be effective; however, there are many barriers to implementation, including, language, ethnic and cultural differences, while a lack of resources and infrastructure play a significant role in a lack of development. More research of this nature is required to provide scientific support for structures and guidelines for the peri-urban community based South African player, to ensure the efficacy of internationally successful interventions such as the Nordic exercise.
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The impact of three different footwear conditions on individual biomechanical, physiological and perceptual responses during running.
- Authors: McDougall, Justin John
- Date: 2016
- Subjects: Running -- Physiological aspects , Running shoes -- Physiological aspects , Running -- Health aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5177 , http://hdl.handle.net/10962/d1019988
- Description: Background: Despite the introduction of running footwear in the 1970’s, running injury rates continue to be unacceptably high. The subsequent revival of barefoot running and the introduction of minimalist footwear occurred, in an attempt to reduce injury rates and increase performance. There is much contention in the literature around the effectiveness of these footwear conditions. Furthermore individual responses have recently been proposed to provide more accurate and reflective conclusions than the use of mean data. Objectives: Twofold: a) to compare the biomechanical, physiological and perceptual responses between the shod, minimalist and barefoot footwear conditions and b) to assess and compare individual responses under these footwear conditions. Methods: 26 well-trained, male, habitually shod endurance runners, aged between 18 - 30 years completed three experimental sessions on an indoor runway and motorized treadmill. Each session was completed in either the shod, minimalist or barefoot condition, running at 15km.h-1. Variables assessed included stride rate, stride length, impact peak, vertical impact and average loading rate and strike time (biomechanical); heart rate, oxygen consumption and electromyography (physiological); and rating of perceived exertion and body discomfort (perceptual). Results: Biomechanics – Stride rate and stride length showed a significant (p<0.001) increase and decrease respectively when running in the minimalist or barefoot conditions versus shod. Running barefoot versus the minimalist and shod conditions resulted in a significantly (p<0.001) greater vertical impact loading rate. Strike time was significantly (p=0.008) reduced running in the minimalist and barefoot conditions versus shod. Physiology – Running barefoot versus shod resulted in a significantly (p=0.02) reduced heart rate and Tibialis Anterior activity (p=0.005). There was a large variability in individual responses for many variables, with responders and non-responders seen. Conclusion: The study suggests that there are significant differences between all three forms of running for some variables. It was further noted that there is support for the proposal that individual responses are highly variable and should be analysed accordingly
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An ergonomics intervention study into the physiological, perceptual and productivity effects of three citrus harvesting bag designs in the Eastern Cape of South Africa : a combined laboratory and field approach
- Authors: Bassey-Duke, Elizabeth Misan
- Date: 2015
- Subjects: Citrus -- Harvesting -- South Africa -- Eastern Cape , Lifting and carrying -- South Africa -- Eastern Cape , Manual work -- South Africa -- Eastern Cape , Blue collar workers -- South Africa -- Eastern Cape , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5176 , http://hdl.handle.net/10962/d1018908
- Description: Background: Agriculture plays a vital role in the economy of any industrially developing country, including South Africa. In the Eastern Cape of South Africa citrus farming is a significant contributor to the local economy (Johnson et al., 2005). The harvesting phase of citrus farming is performed manually and exposes workers to physical risks, which can lead to the development of musculoskeletal disorders. In particular, the standard harvesting bag comprises of a single shoulder strap and promotes asymmetrical load carriage which results in shoulder and lower back pain complaints. The current study compared the physiological (EMG), perceptual (RPE), usability (PUEU) and productivity effects of two new harvesting bag designs (a hip belt and a backpack bag design) to the standard harvesting bag design. This was performed in a laboratory as well as a field setting. Methods (Laboratory phase): 36 participants (12 males and 24 females) were assigned to one worker group. The “tall ladder worker” group was comprised of only males and the “step ladder worker” and “ground worker” group of females. Each participant was required to simulate a citrus harvesting task while utilizing each of the bag designs on different days. On each day/test session, participants performed three harvesting cycles. Muscle activity was measured throughout the entire testing session and RPE were recorded at the end of each cycle. Results (Laboratory phase): The EMG and RPE results indicate that the backpack design was the most ideal design to reduce asymmetry, while the standard harvesting bag design was the worst. Although not significant, there was greater muscle asymmetry (p=0.109) and a significantly higher perceived exertion when using the standard bag (p=0.0004), in comparison to using the backpack. Methods (Field phase): 17 Xhosa-speaking citrus harvesters (6 females and 11 males) participated in this study. Each harvester worked with one of the three bag designs on a different day. Productivity of each worker was assessed every hour by recording the number of bags filled with fruit and at the end of the shift. A Perceived Usefulness & Ease of Use questionnaire was presented to each participant to obtain feedback on worker acceptance to the new bag designs. Results (Field phase): A general trend in support of the hip belt bag design over the other two bag designs were found, even within the different worker demographic groups (age, sex and worker experience). The workers perceived less exertion (7.98 ± 1.86) and were more productive (9.90 ± 2.11 bags/hour) when using the hip belt design; they also found this bag the most useful (1.02 ± 0.09) and easy to use (1.07 ± 0.25). In contrast, the backpack bag design had significantly poorer responses when compared to the other two bag designs and this was evident in all the dependent variables assessed (RPE, productivity and PUEU). Conclusion: The results from the laboratory phase supported the expectation that the backpack bag design reduces asymmetry and hence, is more suitable than the standard harvesting bag. However, results from the field show that the hip belt bag design was the most preferred and the backpack was the least preferred. Bao & Shahnavaz (1989) highlight the need for ergonomics researcher to convey laboratory findings into the field context. However, as shown by the current study, there are numerous challenges associated with field work, making it difficult for laboratory findings to be successfully conveyed to the field. Limitations and Recommendations: For the laboratory phase of the project, no biomechanical and cardiovascular responses were assessed. However, for a holistic approach, these variables should be considered in future studies. Due to high variability from one harvesting cycle to another, more than three harvesting cycles should also be performed to accurately replicate the harvesting process as done in the field over extended durations of time. For the field phase, data should be collected from more than one citrus farm and thus a larger sample size could be obtained. This would improve the validity of the study. In addition to this, data should be collected for a full working day, especially if environmental conditions are not a hindrance, as well as for a whole season, since workloads vary, depending on the time of the harvesting season. , Name on Graduation Programme: Bassey-Duke, Elizabeth Missan
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The acute impact of extended aerobic exercise on cognitive performance
- Authors: Tichiwanhuyi, Tendayi Stephen
- Date: 2015
- Subjects: Aerobic exercises , Cognition -- Effect of exercise on , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Visual perception , Short-term memory , Motor ability , Human information processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5173 , http://hdl.handle.net/10962/d1018182
- Description: Previous research has established a relationship between exercise and cognition, with more emphasis on this ascertained link, being made on the effects of long term and endurance exercise on cognition. However, enhanced worker effectiveness relies on a strong acute collaboration of physical and cognitive performance during task execution. As a result, the purpose of this study was to examine the acute effects of extended aerobic exercise on visual perception, working memory and motor responses, and to achieve this 24 participants (12 males and 12 females) aged between 18 and 24 participated in a 2 bout cycling exercise. The experimental condition had cycling resistance set at 60 percent of each individual’s maximum aerobic output and the control condition had zero cycling resistance, where three cognitive tasks were performed at 10 minute intervals during the cycling exercise. The results showed that exercise did not affect any significant changes on the cognitive performance measures over the entire cycling duration, as well as during the exercise phase (cycling with resistance). However, visual perception improved significantly (p<0.05) immediately after exercise. This led to the conclusion that moderate to high intensity exercise when performed for an extended duration, has selective effects on certain cognitive performance measures, with the time at which the performance is measured during the exercise being a relevant factor to be considered for maximum activation effects of the exercise.
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