Investigating playing-related musculoskeletal disorders in South African instrumental musicians
- Authors: Green, Erryn Mae
- Date: 2024-04-04
- Subjects: Musculoskeletal disorder , Musculoskeletal system Diseases , Musicians Wounds and injuries , Musicians Health and hygiene , Human engineering South Africa , Musicians Health risk assessment , Biomechanics , Musical instruments , Music genre
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435310 , vital:73146
- Description: This study, one of the first studies in SA to investigate PRMD in a wideranging sample of instrumental musicians using a validated self-report tool, shows that PRMDs are highly prevalent among a range of SA musicians and have a considerably negative effect on musicians’ performance ability and quality of life. However, making inferences about most affected genre or instrumental group was challenging due to the small sample sizes in some categories. The results from this study confirm that the nature of PRMD development is indeed multi-factorial, with factors numerous individual and playing-related factors playing a role in the development of PRMDs in SA musicians. Better support and education on health promotion for musicians, including awareness of and prevention strategies for PRMDs in the SA context are needed which may reduce the prevalence of PRMDs. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2024
- Full Text:
- Authors: Green, Erryn Mae
- Date: 2024-04-04
- Subjects: Musculoskeletal disorder , Musculoskeletal system Diseases , Musicians Wounds and injuries , Musicians Health and hygiene , Human engineering South Africa , Musicians Health risk assessment , Biomechanics , Musical instruments , Music genre
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435310 , vital:73146
- Description: This study, one of the first studies in SA to investigate PRMD in a wideranging sample of instrumental musicians using a validated self-report tool, shows that PRMDs are highly prevalent among a range of SA musicians and have a considerably negative effect on musicians’ performance ability and quality of life. However, making inferences about most affected genre or instrumental group was challenging due to the small sample sizes in some categories. The results from this study confirm that the nature of PRMD development is indeed multi-factorial, with factors numerous individual and playing-related factors playing a role in the development of PRMDs in SA musicians. Better support and education on health promotion for musicians, including awareness of and prevention strategies for PRMDs in the SA context are needed which may reduce the prevalence of PRMDs. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2024
- Full Text:
An investigation into the force-EMG relationship for static and dynamic exertions
- Koekemoer, Wesley Agosthinho
- Authors: Koekemoer, Wesley Agosthinho
- Date: 2022-04-06
- Subjects: Electromyography , Force and energy , Muscles Physiology , Biomechanics , Muscle contraction , Isometric exercise , Isotonic exercise , Static and dynamic exertions
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/291076 , vital:56816
- Description: The force-EMG relationship has multiple applications in varying fields of study and practice. One such application is the development of safety guidelines and regulations. Current guidelines are based on static muscle actions even though the majority of tasks encountered in industry are dynamic in nature. This may have negative implications for the health, safety, and productivity of workers as regulations based on static muscle actions may place higher force demands on manual labourers compared to what would be expected if regulations were based on dynamic muscle actions. Regulations based on dynamic muscle actions may be more effective in worker safety as the nature of the regulation matches that of the demand. Few studies have investigated the force-EMG relationship during dynamic muscle actions and the few that do exist have reported contradictory / mixed results. Therefore, the purpose of this study was to: 1) gain an understanding of EMG responses at different load levels, and 2) show how the relationship differs between static and dynamic muscle actions. A two-factorial repeated-measures experiment was developed for this study. Eighteen experimental conditions, utilizing six load levels (0%, 20%, 40%, 60%, 80%, and 100% of maximum voluntary force) for each of the three muscle actions (isometric, concentric and eccentric). Surface EMG responses were obtained under these conditions by repeatedly dorsiflexing and plantarflexing the foot, thus activating the soleus muscle. A maximum voluntary exertion on an isokinetic dynamometer determined the maximum force level, based on which the sub-maximal loads were calculated and added to a pulley system. 31 student participants were recruited for this experiment which was conducted over two sessions – one information and habituation session, and one experimental session. The EMG data recorded were processed and checked for normality and outliers. The data was then analysed via a General Linear Model analysis to determine the effect of exertion type and of load level on the muscle activity. Significant differences were identified at p<0.05 and followed by a Tukey post-hoc test. Correlation analyses were also conducted to determine the relationship between the force and EMG at all three exertion types. All dependent measures showed that as the load level increased so did the sEMG amplitude for all muscle actions. Muscle actions differed significantly between majority of six force levels. Correlations between the load levels and sEMG amplitude for each muscle action indicated a significant correlation with a moderate strength. The conclusion draws from this study that there is a positive correlation between force and sEMG amplitude, at all load levels, with a moderate strength. However, the muscle actions differed significantly from each other. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2022
- Full Text:
- Authors: Koekemoer, Wesley Agosthinho
- Date: 2022-04-06
- Subjects: Electromyography , Force and energy , Muscles Physiology , Biomechanics , Muscle contraction , Isometric exercise , Isotonic exercise , Static and dynamic exertions
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/291076 , vital:56816
- Description: The force-EMG relationship has multiple applications in varying fields of study and practice. One such application is the development of safety guidelines and regulations. Current guidelines are based on static muscle actions even though the majority of tasks encountered in industry are dynamic in nature. This may have negative implications for the health, safety, and productivity of workers as regulations based on static muscle actions may place higher force demands on manual labourers compared to what would be expected if regulations were based on dynamic muscle actions. Regulations based on dynamic muscle actions may be more effective in worker safety as the nature of the regulation matches that of the demand. Few studies have investigated the force-EMG relationship during dynamic muscle actions and the few that do exist have reported contradictory / mixed results. Therefore, the purpose of this study was to: 1) gain an understanding of EMG responses at different load levels, and 2) show how the relationship differs between static and dynamic muscle actions. A two-factorial repeated-measures experiment was developed for this study. Eighteen experimental conditions, utilizing six load levels (0%, 20%, 40%, 60%, 80%, and 100% of maximum voluntary force) for each of the three muscle actions (isometric, concentric and eccentric). Surface EMG responses were obtained under these conditions by repeatedly dorsiflexing and plantarflexing the foot, thus activating the soleus muscle. A maximum voluntary exertion on an isokinetic dynamometer determined the maximum force level, based on which the sub-maximal loads were calculated and added to a pulley system. 31 student participants were recruited for this experiment which was conducted over two sessions – one information and habituation session, and one experimental session. The EMG data recorded were processed and checked for normality and outliers. The data was then analysed via a General Linear Model analysis to determine the effect of exertion type and of load level on the muscle activity. Significant differences were identified at p<0.05 and followed by a Tukey post-hoc test. Correlation analyses were also conducted to determine the relationship between the force and EMG at all three exertion types. All dependent measures showed that as the load level increased so did the sEMG amplitude for all muscle actions. Muscle actions differed significantly between majority of six force levels. Correlations between the load levels and sEMG amplitude for each muscle action indicated a significant correlation with a moderate strength. The conclusion draws from this study that there is a positive correlation between force and sEMG amplitude, at all load levels, with a moderate strength. However, the muscle actions differed significantly from each other. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2022
- Full Text:
An ergonomics study of orthotics and prosthetics workshops in the Eastern Cape of South Africa
- Authors: Mgibantaka, Aviwe Sihle
- Date: 2021-10-29
- Subjects: Orthopedic apparatus industry South Africa Eastern Cape Administration , Prosthesis industry South Africa Eastern Cape Administration , Prosthetists Health and hygiene South Africa Eastern Cape , Prosthetists Job stress South Africa Eastern Cape , Work environment Psychological aspects , Industrial hygiene South Africa Eastern Cape , Human engineering South Africa Eastern Cape , Industrial safety South Africa Eastern Cape , Posture Health aspects
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192108 , vital:45196
- Description: The South African healthcare system is under pressure due to inequalities inherited from the Apartheid system of the past, as well as more recent maladministration. These problems are particularly evident in the Eastern Cape province, which is considered the second poorest province in the country. Furthermore, the rehabilitation sector within healthcare is struggling for recognition in both the public and private healthcare sectors. Orthotists and prosthetists (O&Ps) form an important service in the greater rehabilitation sector since they provide an essential service for people living with disabilities, thus enabling them to function independently. Limited literature and anecdotal evidence suggest that O&Ps perform strenuous physical work under sub-optimal environmental conditions. Furthermore, it is hypothesized that the contextual influences of a struggling healthcare system such as lack or resources, poor referral systems, staff shortages and poor working environments may create a lot of challenges for O&Ps that can impact O&P’s health and well-being and work performance. Purpose: The purpose of this study was to assess the systemic challenges and enablers facing orthotists and prosthetists working in the Eastern Cape of South Africa and thus also evaluate the impact on their health and well-being as well as their job performance. Furthermore, this thesis aimed to compare the work system of O&Ps working in the public with that of O&Ps in the private sector. Methods: A quantitative research method was chosen for this study. Data were collected using a descriptive questionnaire-based approach aimed at identifying the socio-technical interactions in the work systems of O&Ps in the Eastern Cape province of South Africa. This study was approved by the Rhodes University Ethical Standards Committee. The questionnaire was created in Google forms and the link to the online form was sent to Medical O&Ps and Orthopaedic Footwear Technicians using instant messaging (WhatsApp). Two hard copies were also handed out. Data were analysed using StatSoft Statistica Software (version 13.4.0.14 by TIBCO Software Inc.). Descriptive, parametric, content and correlation analyses were conducted. Significant findings were identified at p<0.05. Results: The study received 43 respondents working in both the public and private health sectors, of which 53.5% were males and 46.5% females. The mean age of the respondents was 34.38 years with a coefficient of variation of 19.45%. Majority of respondents (68.9%) worked in the public sector, with the remainder working in the private sector, or sharing their time between both healthcare sectors. Generally, respondents were satisfied with the organizational structure of their workplaces and their work environments. Work demands were identified by respondents from both sectors as an area of concern as tasks performed by O&Ps entailed physical strength, prolonged standing, awkward postures, and repetitive movements. Furthermore, there were some concerns about lighting and noise being unfavourable in some of the workshops. For all the system components, the standard deviations had a low dispersion of less than 1.0 from the mean. The lowest dispersion was 0.63 and the highest dispersion from the mean was 0.99. The analysis using the general linear models option revealed a significant difference between the scores of the work system components (p=0.03). The subsequent Tukey post-hoc test revealed a significant difference in the mean rating scores between the “Environment” and “Work demands”, with a p-value of 0.03. There was discontentment from respondents working in both sectors with their work productivity as the public health sector respondents were 64.52% content; private sector respondents were 68.89% content, and respondents working in both sectors were only 56.67% content. When comparing the responses between O&Ps working in the different sectors, respondents working both sectors were unhappy with the provision of tools, machines, and materials, with 56.25% of the respondents working in the public health sector being less happy than the 61.11% working in the private health sector and the 63.19% working in both the private and public health sectors. Respondents had concerns regarding health and well-being with 60.60% of respondents working in both the public and private health sectors and experiencing more challenges than the 61.05% in the public and 67.24% in the private health sectors, respectively. Correlation analyses revealed very high positive correlations between the system components and the system outcomes. Conclusion: The biggest issue emerging from this study was work demands as O&Ps work is physically demanding. O&Ps had to do a lot of manual handling, heavy load lifting, endure repetitive and vibration movements, prolonged standing and bending in awkward postures to complete tasks. The results from this study indicate that the private health sector is better equipped in terms of the work environment, machines than the public healthcare sector. The finding from this study can be used to improve the factors that enable O&Ps’ job performance and come up with possible solutions to the challenges O&Ps face in their jobs. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2021
- Full Text:
- Authors: Mgibantaka, Aviwe Sihle
- Date: 2021-10-29
- Subjects: Orthopedic apparatus industry South Africa Eastern Cape Administration , Prosthesis industry South Africa Eastern Cape Administration , Prosthetists Health and hygiene South Africa Eastern Cape , Prosthetists Job stress South Africa Eastern Cape , Work environment Psychological aspects , Industrial hygiene South Africa Eastern Cape , Human engineering South Africa Eastern Cape , Industrial safety South Africa Eastern Cape , Posture Health aspects
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192108 , vital:45196
- Description: The South African healthcare system is under pressure due to inequalities inherited from the Apartheid system of the past, as well as more recent maladministration. These problems are particularly evident in the Eastern Cape province, which is considered the second poorest province in the country. Furthermore, the rehabilitation sector within healthcare is struggling for recognition in both the public and private healthcare sectors. Orthotists and prosthetists (O&Ps) form an important service in the greater rehabilitation sector since they provide an essential service for people living with disabilities, thus enabling them to function independently. Limited literature and anecdotal evidence suggest that O&Ps perform strenuous physical work under sub-optimal environmental conditions. Furthermore, it is hypothesized that the contextual influences of a struggling healthcare system such as lack or resources, poor referral systems, staff shortages and poor working environments may create a lot of challenges for O&Ps that can impact O&P’s health and well-being and work performance. Purpose: The purpose of this study was to assess the systemic challenges and enablers facing orthotists and prosthetists working in the Eastern Cape of South Africa and thus also evaluate the impact on their health and well-being as well as their job performance. Furthermore, this thesis aimed to compare the work system of O&Ps working in the public with that of O&Ps in the private sector. Methods: A quantitative research method was chosen for this study. Data were collected using a descriptive questionnaire-based approach aimed at identifying the socio-technical interactions in the work systems of O&Ps in the Eastern Cape province of South Africa. This study was approved by the Rhodes University Ethical Standards Committee. The questionnaire was created in Google forms and the link to the online form was sent to Medical O&Ps and Orthopaedic Footwear Technicians using instant messaging (WhatsApp). Two hard copies were also handed out. Data were analysed using StatSoft Statistica Software (version 13.4.0.14 by TIBCO Software Inc.). Descriptive, parametric, content and correlation analyses were conducted. Significant findings were identified at p<0.05. Results: The study received 43 respondents working in both the public and private health sectors, of which 53.5% were males and 46.5% females. The mean age of the respondents was 34.38 years with a coefficient of variation of 19.45%. Majority of respondents (68.9%) worked in the public sector, with the remainder working in the private sector, or sharing their time between both healthcare sectors. Generally, respondents were satisfied with the organizational structure of their workplaces and their work environments. Work demands were identified by respondents from both sectors as an area of concern as tasks performed by O&Ps entailed physical strength, prolonged standing, awkward postures, and repetitive movements. Furthermore, there were some concerns about lighting and noise being unfavourable in some of the workshops. For all the system components, the standard deviations had a low dispersion of less than 1.0 from the mean. The lowest dispersion was 0.63 and the highest dispersion from the mean was 0.99. The analysis using the general linear models option revealed a significant difference between the scores of the work system components (p=0.03). The subsequent Tukey post-hoc test revealed a significant difference in the mean rating scores between the “Environment” and “Work demands”, with a p-value of 0.03. There was discontentment from respondents working in both sectors with their work productivity as the public health sector respondents were 64.52% content; private sector respondents were 68.89% content, and respondents working in both sectors were only 56.67% content. When comparing the responses between O&Ps working in the different sectors, respondents working both sectors were unhappy with the provision of tools, machines, and materials, with 56.25% of the respondents working in the public health sector being less happy than the 61.11% working in the private health sector and the 63.19% working in both the private and public health sectors. Respondents had concerns regarding health and well-being with 60.60% of respondents working in both the public and private health sectors and experiencing more challenges than the 61.05% in the public and 67.24% in the private health sectors, respectively. Correlation analyses revealed very high positive correlations between the system components and the system outcomes. Conclusion: The biggest issue emerging from this study was work demands as O&Ps work is physically demanding. O&Ps had to do a lot of manual handling, heavy load lifting, endure repetitive and vibration movements, prolonged standing and bending in awkward postures to complete tasks. The results from this study indicate that the private health sector is better equipped in terms of the work environment, machines than the public healthcare sector. The finding from this study can be used to improve the factors that enable O&Ps’ job performance and come up with possible solutions to the challenges O&Ps face in their jobs. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2021
- Full Text:
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.
- Full Text:
- 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.
- Full Text:
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.
- Full Text:
- 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.
- Full Text:
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.
- Full Text:
- 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.
- Full Text:
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
- Bassey-Duke, Elizabeth Misan
- 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
- Full Text:
- 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
- Full Text:
Risk assessment and the effects of overhead work - an automotive industry example
- Authors: Elliott, Andrew Brent
- Date: 2008
- Subjects: Human engineering -- South Africa , Industrial safety -- South Africa , Automobile industry workers -- South Africa -- Health risk assessment , Automobile industry and trade -- South Africa -- Safety measures , Musculoskeletal system -- Wounds and injuries -- Prevention , Lifting and carrying -- Safety measures , Work measurement , Posture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5132 , http://hdl.handle.net/10962/d1005211 , Human engineering -- South Africa , Industrial safety -- South Africa , Automobile industry workers -- South Africa -- Health risk assessment , Automobile industry and trade -- South Africa -- Safety measures , Musculoskeletal system -- Wounds and injuries -- Prevention , Lifting and carrying -- Safety measures , Work measurement , Posture
- Description: The focus of this investigation was an analysis of the work demands being placed on South African automotive industry workers as there is a recognised problem with regard to the prevalence of musculoskeletal disorders (MSDs). Preliminary work was conducted to highlight the dominant risks and areas which elicited higher numbers of MSDs within the chosen automotive plant. An area of concern was highlighted through medical record analysis and the use of risk assessment tools, thereby prioritising the need for ergonomic intervention. In particular, the effects of varying restricted and overhead work heights on the biomechanical, physiological and psychophysical responses of an individual were investigated. Twenty-eight subjects were required to complete sixteen conditions. The conditions consisted of the adoption of restricted and upright overhead static postures, with half requiring the holding of four kilograms of weight in the hands and the remaining eight conditions having no weight. Testing was carried out using an electromyography unit, ergospirometer and a perceptual Body Discomfort Map and Scale. This involved a habituation and testing session. The results of the testing revealed the biomechanical and physiological responses were dependant on the change in height. Body discomfort was also shown to be variable over the changing height conditions. This indicates that there is a significant effect of height on an individual’s responses during overhead work. The extreme restricted (-200mm and -100mm) and upright (+300mm and +400mm) overhead conditions within this study were limiting, as they elicited the highest muscle activation, physiological responses and body discomfort ratings. Positions that are preferable to adopt, which were identified from the results in this study, indicate conditions closer to head height (0mm and +100mm) were favourable. The results therefore illustrate how awkward working postures during work are likely to elicit higher demands from an individual, which could lead to an increased risk for the development of a musculoskeletal disorder. The added factor of weight elicited significant results over all variables, excluding a respiratory The focus of this investigation was an analysis of the work demands being placed on South African automotive industry workers as there is a recognised problem with regard to the prevalence of musculoskeletal disorders (MSDs). Preliminary work was conducted to highlight the dominant risks and areas which elicited higher numbers of MSDs within the chosen automotive plant. An area of concern was highlighted through medical record analysis and the use of risk assessment tools, thereby prioritising the need for ergonomic intervention. In particular, the effects of varying restricted and overhead work heights on the biomechanical, physiological and psychophysical responses of an individual were investigated. Twenty-eight subjects were required to complete sixteen conditions. The conditions consisted of the adoption of restricted and upright overhead static postures, with half requiring the holding of four kilograms of weight in the hands and the remaining eight conditions having no weight. Testing was carried out using an electromyography unit, ergospirometer and a perceptual Body Discomfort Map and Scale. This involved a habituation and testing session. The results of the testing revealed the biomechanical and physiological responses were dependant on the change in height. Body discomfort was also shown to be variable over the changing height conditions. This indicates that there is a significant effect of height on an individual’s responses during overhead work. The extreme restricted (-200mm and -100mm) and upright (+300mm and +400mm) overhead conditions within this study were limiting, as they elicited the highest muscle activation, physiological responses and body discomfort ratings. Positions that are preferable to adopt, which were identified from the results in this study, indicate conditions closer to head height (0mm and +100mm) were favourable. The results therefore illustrate how awkward working postures during work are likely to elicit higher demands from an individual, which could lead to an increased risk for the development of a musculoskeletal disorder. The added factor of weight elicited significant results over all variables, excluding a respiratory individual.
- Full Text:
- Authors: Elliott, Andrew Brent
- Date: 2008
- Subjects: Human engineering -- South Africa , Industrial safety -- South Africa , Automobile industry workers -- South Africa -- Health risk assessment , Automobile industry and trade -- South Africa -- Safety measures , Musculoskeletal system -- Wounds and injuries -- Prevention , Lifting and carrying -- Safety measures , Work measurement , Posture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5132 , http://hdl.handle.net/10962/d1005211 , Human engineering -- South Africa , Industrial safety -- South Africa , Automobile industry workers -- South Africa -- Health risk assessment , Automobile industry and trade -- South Africa -- Safety measures , Musculoskeletal system -- Wounds and injuries -- Prevention , Lifting and carrying -- Safety measures , Work measurement , Posture
- Description: The focus of this investigation was an analysis of the work demands being placed on South African automotive industry workers as there is a recognised problem with regard to the prevalence of musculoskeletal disorders (MSDs). Preliminary work was conducted to highlight the dominant risks and areas which elicited higher numbers of MSDs within the chosen automotive plant. An area of concern was highlighted through medical record analysis and the use of risk assessment tools, thereby prioritising the need for ergonomic intervention. In particular, the effects of varying restricted and overhead work heights on the biomechanical, physiological and psychophysical responses of an individual were investigated. Twenty-eight subjects were required to complete sixteen conditions. The conditions consisted of the adoption of restricted and upright overhead static postures, with half requiring the holding of four kilograms of weight in the hands and the remaining eight conditions having no weight. Testing was carried out using an electromyography unit, ergospirometer and a perceptual Body Discomfort Map and Scale. This involved a habituation and testing session. The results of the testing revealed the biomechanical and physiological responses were dependant on the change in height. Body discomfort was also shown to be variable over the changing height conditions. This indicates that there is a significant effect of height on an individual’s responses during overhead work. The extreme restricted (-200mm and -100mm) and upright (+300mm and +400mm) overhead conditions within this study were limiting, as they elicited the highest muscle activation, physiological responses and body discomfort ratings. Positions that are preferable to adopt, which were identified from the results in this study, indicate conditions closer to head height (0mm and +100mm) were favourable. The results therefore illustrate how awkward working postures during work are likely to elicit higher demands from an individual, which could lead to an increased risk for the development of a musculoskeletal disorder. The added factor of weight elicited significant results over all variables, excluding a respiratory The focus of this investigation was an analysis of the work demands being placed on South African automotive industry workers as there is a recognised problem with regard to the prevalence of musculoskeletal disorders (MSDs). Preliminary work was conducted to highlight the dominant risks and areas which elicited higher numbers of MSDs within the chosen automotive plant. An area of concern was highlighted through medical record analysis and the use of risk assessment tools, thereby prioritising the need for ergonomic intervention. In particular, the effects of varying restricted and overhead work heights on the biomechanical, physiological and psychophysical responses of an individual were investigated. Twenty-eight subjects were required to complete sixteen conditions. The conditions consisted of the adoption of restricted and upright overhead static postures, with half requiring the holding of four kilograms of weight in the hands and the remaining eight conditions having no weight. Testing was carried out using an electromyography unit, ergospirometer and a perceptual Body Discomfort Map and Scale. This involved a habituation and testing session. The results of the testing revealed the biomechanical and physiological responses were dependant on the change in height. Body discomfort was also shown to be variable over the changing height conditions. This indicates that there is a significant effect of height on an individual’s responses during overhead work. The extreme restricted (-200mm and -100mm) and upright (+300mm and +400mm) overhead conditions within this study were limiting, as they elicited the highest muscle activation, physiological responses and body discomfort ratings. Positions that are preferable to adopt, which were identified from the results in this study, indicate conditions closer to head height (0mm and +100mm) were favourable. The results therefore illustrate how awkward working postures during work are likely to elicit higher demands from an individual, which could lead to an increased risk for the development of a musculoskeletal disorder. The added factor of weight elicited significant results over all variables, excluding a respiratory individual.
- Full Text:
- «
- ‹
- 1
- ›
- »