NTRODUCTION Musculoskeletal disorders (MSD) are common in industries worldwide and are a major cause of sick leave, disability and reduced productivity while at work. Many mining-related tasks in South African mines may be associated with MSDs and therefore work-related musculoskeletal disorders are likely to occur in the mining industry. Musculoskeletal disease had hitherto not been researched in the South Africa mining industry and the importance especially as an occupational disease of relevance to the mining industry needed to be considered. Discussion was held within the research tripartite structures; and based on the evidence that musculoskeletal diseases are common in labour-intensive industries worldwide and the South African miners are an ageing population, the need for determining the incidence and associated risk factors was recognized. The Mine Health and Safety Council commissioned this study because there were no studies on musculoskeletal disorders in the South African mining industry. OBJECTIVES The objectives of the study were:  To determine the incidence of musculoskeletal disorders at a South African coal, gold, and platinum mine.  To describe the anatomical sites of MSDs disorders reported by the mineworkers, the occupations and physical activities of these mineworkers and the sick leave and disability associated with the MSD at a South African coal, gold and platinum mine.  To examine associations between MSDs reported by the mineworkers and mental disorders – as measured by the Self Reporting Questionnaire-20 (SRQ-20)-, significant life events (health, assault, fright and financial problems) and social functioning (personal and work relationships and ability to relax).  To examine the association between MSDs reported by mineworkers and their home language.  To examine the association between MSDs reported by the mineworkers and usual and recent physical activities at work. METHOD The study had a mixed design i.e. an incidence study to identify mineworkers presenting to the mines’ primary care clinic with a musculoskeletal disorder and a nested case-control study involving consenting cases to investigate associations between musculoskeletal disorders and risk factors. At three South African mines (a coal mine, a gold mine and a platinum mine), mineworkers presenting to a mine clinic with a musculoskeletal disorder were recorded over a six month period. Complaints arising from acute traumatic injury (e.g. crush injuries, fractures, bruises, dislocations or amputations) were excluded. Mineworkers presenting with a medical condition not related to a musculoskeletal disorder or symptom were selected as controls. A standardized Nordic questionnaire was used to analyse musculoskeletal symptoms. The Southampton Examination Schedule was used to examine mineworkers presenting with neck and upper limb pain. The Self-Reporting Questionnaire was used to establish a possible mental disorder. Questions adapted from the Life Events and Difficulties Schedule and a rating scale for Social Functioning were used to determine psychosocial factors. Home language spoken by mineworkers was also recorded. Trained research nurses administered questionnaires to participating subjects in their preferred language. RESULTS Six hundred and ninety one cases identified at the three primary care clinics at the coal (70 cases), gold (329 cases) and platinum mine (292 cases) were included in this study. Seven hundred and one controls were identified: 81 at the coal mine, 345 at the gold mine and 275 at the platinum mine. The percentages of mineworkers employed on the mine presenting to the mine clinic with a musculoskeletal disorder over the six months of the study were 7.0% at the coal mine, 5.4% at the gold mine and 8.1% at the platinum mine. A more conservative estimate was obtained using only mineworkers who presented during office hours and who had the musculoskeletal disorder confirmed by a research nurse (termed MSD cases). The percentage of MSD cases over the six months of the study was 6.5% at the coal mine, 1.9% at the gold mine and 4.1% at the platinum mine and these data suggest an annual incidence of 130/1000, 38/1000 and 82/1000 for the coal, gold and platinum mines respectively. Lower limb pain was the most common musculoskeletal presentation at the platinum mine and at the coal and gold mine it was lower back pain. At the platinum mine, almost all the cases (96.2%) had disabling symptoms; at the gold mine and coal mine it was 65.3% and 47.1% respectively. Experience of an extremely frightening event increased the odds ratio for a musculoskeletal disorder of the upper limb, lower back and lower limb in the univariate, multivariate analyses and final models at the gold and platinum mine. A possible mental disorder (i.e. high Self-Reporting Questionnaire score) was consistently found to be negatively associated with upper limb pain, lower back pain and lower limb pain. No consistent associations were found between home language (a surrogate for ethnicity) and musculoskeletal disorders except for the upper limb. Kneeling was the only physical activity significantly associated with lower limb pain. Upper limb A recent medical diagnosis (OR = 2.6; 95% 1.2-5.7), speaking Southern Sotho (OR = 2.5; 95% CI 1.1-5.7) or Other Language (OR = 2.0; 95% CI 1.6-2.4) – i.e. Swazi, Afrikaans, Ndebele, Tswana, Portuguese, English, Tsonga or Mpondo - and working on the surface (OR =2.6; 95% CI 1.1-6.0) were associated with upper limb pain. The work activity that involved barring (OR = 0.6; 95% CI 0.4-0.9), working both on the surface and underground (OR = 0.7; 95% CI 0.5-0.8) and having a possible mental disorder (OR = 0.4; 95% CI 0.2-0.5) were negatively associated with musculoskeletal disorders of the upper limb. Lower back pain The risk factors identified were increased age and working on the surface (OR = 2.3; 95% CI 1.9-2.7). Having a possible mental disorder (OR = 0.4; 95% CI 0.4-0.5) and work activity that involved pushing (OR = 0.7; 95% CI 0.5-0.9) were negatively associated. Lower limb pain The risk factors identified were: working at a platinum mine (OR = 2.5; 95% CI 2.1-2.9), increasing age i.e. 45 years and older (OR = 3.5; 95% CI 1.0-12.4), working on the surface (OR = 2.4; 95% CI 1.02-5.6) and the physical activity of kneeling (OR = 2.9; 95% CI 1.6-5.1). Having a possible mental disorder was the only factor that was negatively associated with lower limb pain. A percentage of controls selected had had a diagnosis of musculoskeletal disorders in the past year or longer and this may have diluted associations found (i.e. 29.3% of controls had a history upper limb pain, 49.7% of controls had a history of back pain and 22% of controls had a history of lower limb pain). Therefore, the final model for each anatomical region was adjusted by including an adjustment factor (i.e. history of musculoskeletal disorder) to determine the effect a past MSD would have on the ORs. When the additional models were compared with the final model with all the controls, there were small non-significant differences for a few of the ORs while most ORs were very similar to the model including all controls without the adjustment. DISCUSSION This is the first study to determine the incidence of musculoskeletal disorders in mining in South Africa, and one of few globally in the industry. The research considered risk factors for presenting with a musculoskeletal disorder in three body regions (upper limb, lower back and lower limb). Its strengths included the large range of explanatory variables considered, which included work-related and individual characteristics. Uniquely, report of a frightening event was strongly associated with musculoskeletal disorders (at the gold and platinum mine) and a possible mental disorder was not. The estimated incidence of musculoskeletal disorders was considered high at all three mines with 6.2% of employed mineworkers presenting with a new episode of musculoskeletal pain during the study period. The United States’ Mine Health and Safety Administration database found that the incidence before technological advancements (1983-1984) was 5% and after technological advancements were implemented (2003-2004) had decreased to 4%. The highest percentage of musculoskeletal disorders at the coal and gold mine was from lower back pain. However, at the platinum mine, lower limb pain was the most common musculoskeletal disorder presentation. Surprisingly, no physical activity was found to increase the odds of presenting with upper limb or lower back pain. The reasons for this could be the large percentage of controls who had previously had upper limb or lower back pain; cases and controls preforming similar tasks; or causative exposures had been modified or workers were transferred to ‘light duty’ due to a previous MSD. However, kneeling increased the mineworkers’ odds of presenting with a lower limb disorder. This finding has been reported previously where restrictive work areas due to low ceiling height (in stope panels, for example) cause workers to perform tasks in the kneeling position, resulting in excessive pressure on the knees from body weight. Nearly 10% of cases had a possible mental disorder compared to 15.3% of controls (according to the Self-Reporting Questionnaire). Having a possible mental disorder was found to be consistently negatively associated with upper limb, lower back and lower limb pain. The reasons for this finding are unclear, further research is needed. The controls’ clinical conditions may have been associated with a possible mental disorder (for example HIV and other chronic medical conditions) or the Self-Reporting Questionnaire may not be reliable or sensitive enough for the study population. Experiencing an extremely frightening event and a recent diagnosis of a mental condition were two life events from the Life Events and Difficulties Schedule that were found to increase the odds of presenting with musculoskeletal disorders in this study. The reason or source of the fright could not be determined nor whether the fright was recurrent, prolonged or a single extreme episode which is a limitation of this finding. Working underground can be potentially frightening. Frequent earth tremors, the real threat of rock falls and consistently looking for fault lines, and activities required to secure the roof above the mineworker are part of the job, especially at the gold and platinum mine. Language is likely to be a weak surrogate for ethnicity and in this study was used in an exploratory sense. Industrialisation, urbanization, migration, and electronic media and social affiliations throughout South Africa are in a state of rapid transformation, internalising one another’s values and beliefs which make defining an ethnic group difficult. IMPLICATION FOR POLICY AND PRACTICE There is a growing understanding that mechanical overload may not be the leading cause of regional musculoskeletal pain. Therefore, both work and non-work related factors need to be considered in order to develop multifaceted interventions and programmes. The aim would be to reduce the incidence and disability of musculoskeletal disorders. Important considerations for future research in the mining industry are also discussed. Limitations of and gaps identified in this study are addressed in future research to further our understanding of a very important and potentially manageable condition.

No description available.

Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 102-133).

Thesis (Ph. D.)--University of Missouri--Columbia, 2003. / "December 2003." Typescript. Vita. Includes bibliographical references (leaves 63-74). Also issued on the Internet.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 105-111).

Experiments have been designed to investigate the physiological factors influencing the interrelationship between excitation and force generation that may counteractt he processesle ading to a decline in force (fatigue) during stimulatedi sometric contractions of the human adductor pollicis in vivo. Indices of isometric force, relaxation and contraction rates and evoked compound muscle action potentials (CMAP) were measured during defined patterns of stimulated activity (via the motor nerve). A computerized stimulator controller for precise generation of trains of electrical impulses was developed for this purpose. Forces generated at different frequencies were reproducible on separate occasions. Using an ascending frequency stimulation protocol (1-100Hz) the relationship between force decline and excitation (measured as the amplitude of the surface evoked CMAP) appeared to be dependent on stimulation frequency during ischaemic and nonoccluded activity. At high frequencies (50-100Hz), a `safety factor' was apparent, allowing preservation of force despite a marked fall in excitation, whereas at low frequencies (1-10Hz) force initially potentiated and then declined in excess of excitation. Maximum relaxation rate was reduced at all stimulation frequencies and was independent of stimulation frequency. Contractile activity performed was shown to be linearly related to maximum relaxation rate over a frequency range of 20-100Hz for up to 30max. seconds. Contractile activity performed was therefore used as a measure of the metabolic cost of a contraction. Force failure appeared to depend upon the numbers of stimuli delivered, independent of frequency, rather than on contractile activity performed, suggesting that electrophysiological factors are of importance in contributing to fatigue. Further studieso n CMAP characteristicsd emonstrateda broadeningo f the action potential, reflecting a slowing of conduction velocity, which is thought to lead to `runin' of action potentials, and hencet he reduction of CMAP amplitude associatedw ith the high-frequency `safety factor'. The broadening of the action potential recovered immediately during ischaemic conditions at 100Hz following 2400 stimuli but did not recover following prolonged activity at 20Hz until circulation was restored, whereas CMAP amplitude recovered immediately at both frequencies, suggesting that slowing of conduction velocity may be dependent on metabolic factors at low stimulation frequencies which in turn may depend on the contractile history of the muscle. Patients with myophosphorylase deficiency (and thus unable to utilize glycogen), were studied to investigate the importance of energy supply. A failure of ischaemic recovery of the CMAP amplitude and no broadening of the CMAP after stimulated activity at 20Hz was observed, suggesting a failure of excitation of individual muscle cells occurs resulting in force failure in these individuals. Reversing the pattern of stimulation resulted in an initial enhancement of low frequency (10Hz) force and a prolonged maintenance of this force throughout the period of contraction studied. This was independent of slowing of relaxation or excitation. The initial force enhancement may result from the increased slowing of relaxation, and in addition, a form of post-tetanic twitch potentiation operates to counteract the decline in force despite a loss in excitation. In conclusion, during stimulated contractile activity of the adductor pollicis, mechanisms act to maintain or increase force generated per action potential distal to the sarcolemmal membrane, at both high and low frequencies of stimulation, thereby counteracting mechanisms that lead to fatigue. It is postulated that the alterations in intramuscular processes may allow voluntary isometrically contracting muscle to optimize force production at the onset of a contraction where high motor unit discharge rates are initially developed, delaying or eliminating the influence of excitation failure which would lead to contractile failure once maximal force is achieved, and subsequently to optimize contractile activation in the light of possible excitation failure as motor unit discharge rates decline. These findings may have important functional implications and may form the basis of physiological strategies for optimizing force production in the development of stimulation regimes for `functional electrical stimulation' or to any area of skeletal muscle research in which fatigue resistance is of importance.

No description available.

No description available.