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:
- Date Issued: 2016
- 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:
- Date Issued: 2016
Leopard population density and community attitudes towards leopards in and around Debshan Ranch, Shangani, Zimbabwe
- Authors: Nyoni, Phumuzile
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5946 , http://hdl.handle.net/10962/d1020838
- Description: Leopards (Panthera pardus) are regarded as one of the most resilient large carnivore species in the world and can persist in human dominated landscapes, areas with low prey availability nd highly fragmented habitats. However, recent evidence across much of their range reveals declining populations. In Zimbabwe, 500 Convention for the International Trade in Endangered Species (CITES) export tags are available annually for leopards as hunting trophies, despite limited accurate data on the leopard populations of the country. Moreover, when coupled with the massive land conversions under the controversial National Land Reform Programme (NLRP), leopard populations in Zimbabwe are in dire need of assessment. My study was conducted on Debshan ranch, Shangani, Zimbabwe, which is a commercial cattle (Bos indicus) ranch but also supports a high diversity of indigenous wildlife including an apparently healthy leopard population. However, the NLRP has resulted in an increase in small-holder subsistence farming communities around the ranch (the land was previously privately owned and divided into larger sub-units). This change in land-use means that both human and livestock densities have increased and the potential for human leopard conflict has increased. I estimated the leopard population density of the ranch and assessed community attitudes towards leopards in the communities surrounding the ranch. To estimate population densities, I performed spoor counts and conducted a camera trapping survey. Questionnaire interviews were used to assess community attitudes. My spoor counts provided a leopard density estimate of 13.57 leopards/100km2 compared to the camera trapping estimate of between 2.0 and 6.9 leopards/100km2. Although the high density estimate derived from the spoor counts is possible for Debshan because leopards are the apex predators and are adequately protected, potential edge effects are not yet fully understood. Thus, the more conservative estimate of 2.0 leopards/100km2, derived from the camera trapping survey, is probably more appropriate. Attitudes towards predators amongst respondents surrounding Debshan (n = 140) were neither too negative nor positive, attitude index had a mean score of 1.7 ± 3.8 (range: -7 – 10). No single predictor variable used in my analysis was able to adequately explain why the communities held these negative views. However, livestock losses were repeatedly listed by respondents as being one of the main reasons for their lack of tolerance towards predators. The density estimate of 2.0 leopards/100km2 translates to a population of 9 – 26 leopards within Debshan ranch. This density estimate is too low considering the habitat type at Debshan ranch but should be interpreted with caution as it lacks fundamental elements like age and sex ratio. Moreover, the interaction of the leopard population with the surrounding communities is currently unclear. As a precautionary measure, I recommended reducing the annual hunting quota for Debshan from five to one leopard. Future work should aim to improve the attitudes of the surrounding communities to secure broader landscapes for leopard conservation while also reconciling density estimates to fully understand the leopard population of the region.
- Full Text:
- Date Issued: 2016
- Authors: Nyoni, Phumuzile
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5946 , http://hdl.handle.net/10962/d1020838
- Description: Leopards (Panthera pardus) are regarded as one of the most resilient large carnivore species in the world and can persist in human dominated landscapes, areas with low prey availability nd highly fragmented habitats. However, recent evidence across much of their range reveals declining populations. In Zimbabwe, 500 Convention for the International Trade in Endangered Species (CITES) export tags are available annually for leopards as hunting trophies, despite limited accurate data on the leopard populations of the country. Moreover, when coupled with the massive land conversions under the controversial National Land Reform Programme (NLRP), leopard populations in Zimbabwe are in dire need of assessment. My study was conducted on Debshan ranch, Shangani, Zimbabwe, which is a commercial cattle (Bos indicus) ranch but also supports a high diversity of indigenous wildlife including an apparently healthy leopard population. However, the NLRP has resulted in an increase in small-holder subsistence farming communities around the ranch (the land was previously privately owned and divided into larger sub-units). This change in land-use means that both human and livestock densities have increased and the potential for human leopard conflict has increased. I estimated the leopard population density of the ranch and assessed community attitudes towards leopards in the communities surrounding the ranch. To estimate population densities, I performed spoor counts and conducted a camera trapping survey. Questionnaire interviews were used to assess community attitudes. My spoor counts provided a leopard density estimate of 13.57 leopards/100km2 compared to the camera trapping estimate of between 2.0 and 6.9 leopards/100km2. Although the high density estimate derived from the spoor counts is possible for Debshan because leopards are the apex predators and are adequately protected, potential edge effects are not yet fully understood. Thus, the more conservative estimate of 2.0 leopards/100km2, derived from the camera trapping survey, is probably more appropriate. Attitudes towards predators amongst respondents surrounding Debshan (n = 140) were neither too negative nor positive, attitude index had a mean score of 1.7 ± 3.8 (range: -7 – 10). No single predictor variable used in my analysis was able to adequately explain why the communities held these negative views. However, livestock losses were repeatedly listed by respondents as being one of the main reasons for their lack of tolerance towards predators. The density estimate of 2.0 leopards/100km2 translates to a population of 9 – 26 leopards within Debshan ranch. This density estimate is too low considering the habitat type at Debshan ranch but should be interpreted with caution as it lacks fundamental elements like age and sex ratio. Moreover, the interaction of the leopard population with the surrounding communities is currently unclear. As a precautionary measure, I recommended reducing the annual hunting quota for Debshan from five to one leopard. Future work should aim to improve the attitudes of the surrounding communities to secure broader landscapes for leopard conservation while also reconciling density estimates to fully understand the leopard population of the region.
- Full Text:
- Date Issued: 2016
Stratigraphy and sedimentology of the Msikaba formation in KwaZulu Natal South Coast, South Africa
- Authors: Busakwe, Nolukholo Sinovuyo
- Date: 2015
- Subjects: Geology, Stratigraphic Sedimentology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2501 , vital:27877
- Description: The Msikaba Formation is a Late Devonian fluvial and marine succession which outcrops from Hibberdene to Port Edward along the south coast of KwaZulu-Natal Province, South Africa. The Formation is composed of brownish conglomerate at the bottom and white-greyish quartz arenite sequence in the middle and mixed quartz-arenite with feldspathic sandstone in the upper sequence. Previous studies put more emphasis on the correlation of Msikaba Formation with the Natal Group and Cape Supergroup, whereas this study revised the stratigraphy, and also put new insight on the petrography, sedimentary facies, depositional environments and diagenesis of the Formation. The total stratigraphic section attains a thickness of 184 m at Margate area and 186 m at Port Edward area. The stratigraphy of Msikaba Formation is well exposed on the outcrops along the KwaZulu-Natal coastline. The stratigraphy is subdivided into 4 new members along Margate to Shelly beach section; namely Manaba Member, Uvongo Member, Mhlangeni Member and Shelly Beach Member from bottom upward. Twelve sedimentary facies were identified and the sedimentary facies were integrated into 4 facies association: Facies association 1 (Gmm+Sm) represents braided fluvial deposits, Facies association 2 (Gcm+St+Sp+Sl+Shb) represents tidal channel and tidal flat deposit, Facies association 3 (St+Sp+Sr+Sl) is result of shallow marine deposit and Facies association 4 (Sp+Sl+St+Sm) is a mixed marine and fluvial deposit. Each facies association represents a specific stratigraphic unit and were deposited in a specific sedimentary environment. Grain size analysis was conducted on seventeen thin sections and 500 grains were counted from each thin section. The sandstone grain size parameters of mean, sorting, skewness and kurtosis fell under the average of 0.75, 0.78, 0.4 and 1.2φ respectively. The results show that most of the grain size are coarse to medium grained throughout the study areas and sorting of the sandstones are moderate to poorly sorted. The cumulative frequency diagrams and bivariate plots show positive skewness and negative kurtosis, which indicate a high hydrodynamic environment. Modal composition analysis and petrography studies show that detrital components of the Msikaba Formation are dominated by monocrystalline quartz, feldspar (mostly K-feldspar) and lithic fragments of igneous and metamorphic rocks. The sandstones could be classified as quartz arenite, sub-arkosic sandstone and feldspathic litharenite; and the provenance analysis indicates that the sandstones were derived from craton interior, recycled or quartzose recycled sources which may derived from weathering and erosion of igneous and metamorphic rocks. Diagenetic processes of the Msikaba Formation have been passed through early, mid- and late diagenetic stages. Cementation, mineral conversion and compaction affect early diagenetic stage; authigenic minerals, quartz and feldspar overgrowth are presented in mid-diagenetic stage, whereas recrystallization, replacement, deformation and dissolution have been strongly affected late diagenetic stage. Microscopy, XRD and SEM-EDX studies have identified five types of cements including smectite clay, kaolinite, hematite, quartz and feldspar cements. Quartz cement, pore-filling and pore-lining clay are the major type of cements in the Msikaba Formation. Based on the lithology, sedimentary structure and facies variations, the Manaba Member was most probably deposited in a braided fluvial environment, the Uvongo Member was deposited in a tidal channel environment, the Mhlangeni Member was formed in shallow marine storm-influenced environment, whereas the Shelly Beach Member was represented mixed marine and fluvial environment. The sequence stratigraphy of Msikaba Formation constitutes a transgressive sequence from Manaba Member to Uvongo Member, whereas it ended as a regressive sequence from Mhlangeni Member to Shelly beach Member. The Msikaba Formation shows major differences with the Natal Group and Table Mountain Group (Cape Supergroup) in the lithology, stratigraphic sequence, sedimentary structures, facies system, palaeocurrent styles, fossil contents and depositional environments, which demonstrate that they are not the equivalent stratigraphic unit. Therefore, the Msikaba Formation is a separate, younger stratigraphic unit, and cannot correlate with the Natal Group and Table Mountain Group as suggested by previous researchers.
- Full Text:
- Date Issued: 2015
- Authors: Busakwe, Nolukholo Sinovuyo
- Date: 2015
- Subjects: Geology, Stratigraphic Sedimentology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2501 , vital:27877
- Description: The Msikaba Formation is a Late Devonian fluvial and marine succession which outcrops from Hibberdene to Port Edward along the south coast of KwaZulu-Natal Province, South Africa. The Formation is composed of brownish conglomerate at the bottom and white-greyish quartz arenite sequence in the middle and mixed quartz-arenite with feldspathic sandstone in the upper sequence. Previous studies put more emphasis on the correlation of Msikaba Formation with the Natal Group and Cape Supergroup, whereas this study revised the stratigraphy, and also put new insight on the petrography, sedimentary facies, depositional environments and diagenesis of the Formation. The total stratigraphic section attains a thickness of 184 m at Margate area and 186 m at Port Edward area. The stratigraphy of Msikaba Formation is well exposed on the outcrops along the KwaZulu-Natal coastline. The stratigraphy is subdivided into 4 new members along Margate to Shelly beach section; namely Manaba Member, Uvongo Member, Mhlangeni Member and Shelly Beach Member from bottom upward. Twelve sedimentary facies were identified and the sedimentary facies were integrated into 4 facies association: Facies association 1 (Gmm+Sm) represents braided fluvial deposits, Facies association 2 (Gcm+St+Sp+Sl+Shb) represents tidal channel and tidal flat deposit, Facies association 3 (St+Sp+Sr+Sl) is result of shallow marine deposit and Facies association 4 (Sp+Sl+St+Sm) is a mixed marine and fluvial deposit. Each facies association represents a specific stratigraphic unit and were deposited in a specific sedimentary environment. Grain size analysis was conducted on seventeen thin sections and 500 grains were counted from each thin section. The sandstone grain size parameters of mean, sorting, skewness and kurtosis fell under the average of 0.75, 0.78, 0.4 and 1.2φ respectively. The results show that most of the grain size are coarse to medium grained throughout the study areas and sorting of the sandstones are moderate to poorly sorted. The cumulative frequency diagrams and bivariate plots show positive skewness and negative kurtosis, which indicate a high hydrodynamic environment. Modal composition analysis and petrography studies show that detrital components of the Msikaba Formation are dominated by monocrystalline quartz, feldspar (mostly K-feldspar) and lithic fragments of igneous and metamorphic rocks. The sandstones could be classified as quartz arenite, sub-arkosic sandstone and feldspathic litharenite; and the provenance analysis indicates that the sandstones were derived from craton interior, recycled or quartzose recycled sources which may derived from weathering and erosion of igneous and metamorphic rocks. Diagenetic processes of the Msikaba Formation have been passed through early, mid- and late diagenetic stages. Cementation, mineral conversion and compaction affect early diagenetic stage; authigenic minerals, quartz and feldspar overgrowth are presented in mid-diagenetic stage, whereas recrystallization, replacement, deformation and dissolution have been strongly affected late diagenetic stage. Microscopy, XRD and SEM-EDX studies have identified five types of cements including smectite clay, kaolinite, hematite, quartz and feldspar cements. Quartz cement, pore-filling and pore-lining clay are the major type of cements in the Msikaba Formation. Based on the lithology, sedimentary structure and facies variations, the Manaba Member was most probably deposited in a braided fluvial environment, the Uvongo Member was deposited in a tidal channel environment, the Mhlangeni Member was formed in shallow marine storm-influenced environment, whereas the Shelly Beach Member was represented mixed marine and fluvial environment. The sequence stratigraphy of Msikaba Formation constitutes a transgressive sequence from Manaba Member to Uvongo Member, whereas it ended as a regressive sequence from Mhlangeni Member to Shelly beach Member. The Msikaba Formation shows major differences with the Natal Group and Table Mountain Group (Cape Supergroup) in the lithology, stratigraphic sequence, sedimentary structures, facies system, palaeocurrent styles, fossil contents and depositional environments, which demonstrate that they are not the equivalent stratigraphic unit. Therefore, the Msikaba Formation is a separate, younger stratigraphic unit, and cannot correlate with the Natal Group and Table Mountain Group as suggested by previous researchers.
- Full Text:
- Date Issued: 2015
The relationship between religion/spirituality and the general psychological well-being of the institutionalized elderly population in the Eastern Cape, South Africa
- Authors: Walton, Karen Lynn
- Date: 2015
- Subjects: Psychology, Religious Psychology and religion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5708 , vital:29366
- Description: Psychological well-being has a number of known benefits and is important for the quality of life of the elderly in particular. South Africa can be considered a religious country with the majority of citizens identifying with some religious orientation. The elderly are considered to be a more religious segment of the population, leading to a quantitative exploratory study being undertaken in order to ascertain whether a correlation exists between psychological well-being and religiosity/spirituality in the elderly institutionalised population of South Africa. The General Psychological Well-Being Scale and ASPIRES was administered to a convenience sample of 336 participants in the Eastern Cape Province. A significant but weak positive correlation was found between the variables of psychological well-being and religiosity. A difference was also found between White and African participants’ level of psychological well-being. An ANOVA was performed on the demographic information collected from participants. It was found that higher levels of education and access to private medical care were associated with higher levels of psychological well-being. A regression analysis was also performed on the data. It was found that although religiosity/spirituality does account for some of the variance, there were still a large number of other factors that influence psychological well-being in the elderly that were not captured in this study. Limitations of the study are that the results can’t be generalised to elderly residing at home. All of the participants also lived in urban areas and so differences may be found with rural elderly. Some further directions for research are discussed.
- Full Text:
- Date Issued: 2015
- Authors: Walton, Karen Lynn
- Date: 2015
- Subjects: Psychology, Religious Psychology and religion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5708 , vital:29366
- Description: Psychological well-being has a number of known benefits and is important for the quality of life of the elderly in particular. South Africa can be considered a religious country with the majority of citizens identifying with some religious orientation. The elderly are considered to be a more religious segment of the population, leading to a quantitative exploratory study being undertaken in order to ascertain whether a correlation exists between psychological well-being and religiosity/spirituality in the elderly institutionalised population of South Africa. The General Psychological Well-Being Scale and ASPIRES was administered to a convenience sample of 336 participants in the Eastern Cape Province. A significant but weak positive correlation was found between the variables of psychological well-being and religiosity. A difference was also found between White and African participants’ level of psychological well-being. An ANOVA was performed on the demographic information collected from participants. It was found that higher levels of education and access to private medical care were associated with higher levels of psychological well-being. A regression analysis was also performed on the data. It was found that although religiosity/spirituality does account for some of the variance, there were still a large number of other factors that influence psychological well-being in the elderly that were not captured in this study. Limitations of the study are that the results can’t be generalised to elderly residing at home. All of the participants also lived in urban areas and so differences may be found with rural elderly. Some further directions for research are discussed.
- Full Text:
- Date Issued: 2015
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