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
- Full Text:
- 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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