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Computer technology has advanced rapidly in the past few decades and computers have become a very important and powerful tool in our everyday lives. Prolonged computer use by office workers has been reported to result in an increased risk of developing Work-related Neck and Upper Limb Disorders (WRNULD) (Bernard et al.. 1994: Faucett & Rempel. 1994: Tittiranonda et al.. 1999). The occupational risk factors associated with prolonged computer use include static posture and the speed and force of keyboard operation. Past studies have examined different aspects of these risk factors through measuring muscle electrical activity (EMG), kinematics and keyboard forces. However, most of these studies have been conducted on healthy painfree subjects and even the few Case-Control studies have not clearly established any direct relationships between the risk factors and WRNULD. The present research project consisted of a series of three studies aimed at investigating whether there were intrinsic differences among different individuals in response to different physical stressors. These intrinsic differences may have important implications to help explain why some individuals would develop WRNULD while others do not. The individuals' responses to the demands of three physical stressors: static posture, speed and force of keyboard operation were assessed. The internal exposure measures of kinematics, EMG, keyboard dynamics and subjective discomforts were used to evaluate the inter-individual differences. Study I was a field investigation comparing the neck-shoulder kinematics between symptomatic ("Case", n=8) and asymptomatic ("Control", n=8) office workers. Results showed trends for consistently greater head tilt and neck flexion angles, and greater ranges of movements in the Case Group than the Control Group. / The Case Group also exhibited a trend for increased acromion protraction compared to the Control Group. The Case Group also reported significantly greater discomfort scores compared to the Control Group. Neither the discomforts nor the kinematics displayed any significant changes over a working day. Study 2 was a laboratory study comparing the responses of Case and Control Groups in terms of EMG, kinematics and subjective discomforts, while a standardised computer task was performed continuously for one hour. The responses of Case (n=23) and Control (n=20) Groups were compared to examine the effects of static posture. The results showed similar trends to those in Study I, with increased neck flexion mean angles and ranges of movements in the Case Group compared to the Control Group. In terms of EMG results, there were trends for EMG amplitude differences in the right upper trapezius (UT) and cervical erector spinae (CES) muscles between Case and Control Groups. These trends became statistically significant when the Case subjects were sub-divided into the High (n=15) and Low (n=8) Groups based on their mean discomfort scores. Study 3 was also a laboratory study to compare the Case (n=21) and Control (n=20) Groups when they were challenged by the physical stressors of speed and force of keyboard operation. In this study, each subject's EMG and discomforts were examined in three typing conditions of normal speed and force, increased typing speed and increased typing force. The Case Group showed trends for higher increases in both UT and CES muscle activities than the Control Group, and when divided into the High-Low Groups, the High Group (n=8) showed trends for much higher muscle activities in all three conditions. / Beside muscle activity changes, the High Group subjects also demonstrated a trend for much higher within-subject Speed and Force Variabilities in their keystroke performance, compared to the Low Group and the Control Group. This result implied that the High Group subjects had a more erratic motor control of the keystroke actions. Based on these results, conceptual models were developed to describe the relationships among the physical stressors, internal exposure responses and discomforts. The Altered Motor Control Model refers to the programmed changes in motor control strategies involving muscle recruitment and joint movement patterns, and these changes were closely related to the subjects' musculoskeletal discomforts. The Heightened Sensitivity Model describes the higher sensitivity levels of individuals with more severe discomforts, in response to the demands of physical stressors. These models are closely related and heightened sensitivity may be an 'effect-modifier" of the motor control mechanisms and the perception of discomforts or pains within the individual. In conclusion, the present research has identified important differences between individuals on the basis of their motor control strategies which may contribute to the development of WRNULD. While the present research has mainly examined the individual responses to three physical stressors, it is possible that the models developed may be applicable to other physical stressors. These findings may also have important implications for future ergonomic research, emphasising the need to address interindividual differences in ergonomic interventions to workers. Further research should be directed towards better understanding of these intrinsic individual differences in both physical and non-physical factors that contribute to the development of WRNULD.

Abstract Background: Musculoskeletal discomfort is common among professional orchestra musicians and according to the literature some anatomical areas, such as the neck, upper back and upper extremities, seem to be more frequently affected than others. There are also suggestions made that general joint hypermobility could be a potential risk factor for musculoskeletal discomfort among musicians. Furthermore, there seems to be a higher perceived feeling of psychosocial demands and stress among musicians in comparison to the general workforce. Aim: Investigate the prevalence of, and associations between, musculoskeletal discomfort, general joint hypermobility, psychosocial factors and stress among Swedish big band musicians. A further aim was to investigate associations between musculoskeletal discomfort, general joint hypermobility, psychosocial factors and stress, respectively. Method & Material: This study was part of a larger national survey on professional orchestra musicians in Sweden. This study focused on professional jazz musicians and included data from all three professional big bands in Sweden. The study presents the prevalence of musculoskeletal discomfort, general joint hypermobility, psychosocial factors and stress among professional Swedish big band musicians. 32 musicians completed the survey. Results: The study showed a high prevalence of musculoskeletal discomfort and general joint hypermobility. There were no statistically significant relationships between musculoskeletal discomfort and general joint hypermobility but between psychosocial demands and musculoskeletal discomfort in the anatomical subgroup low back/hip, and between negative stress and musculoskeletal discomfort in the anatomical subgroup low back/hip. Conclusion: In accordance with existing studies on classical orchestra musicians, this study found a high prevalence of musculoskeletal discomfort and general joint hypermobility among Swedish big band musicians. There was a statistically significant association with the relationship between psychosocial demands and musculoskeletal discomfort in the anatomical subgroup low back/hip and between negative stress and musculoskeletal discomfort in the anatomical subgroup low back/hip. Key words: big band musicians, musculoskeletal discomfort, general joint hypermobility, psychosocial factors, stress.

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Content removed due to copyright restrictions: Appendix 6: Paper presented at the 15th New Zealand Ergonomics Society Conference: Ergonomics for the Ageing Population, Martinborough. Scuffham, A., Stevenson, M., Legg, S. & Firth, E. Prevalence of musculoskeletal discomfort in New Zealand small animal veterinarians. In: 15th New Zealand Ergonomics Society Conference: Ergonomics for the Ageing Population. Eds R. G. Adank & L. Gardner Wood. Martinborough, New Zealand Ergonomics Society. 27-28 May, 2009, [CD-ROM]. Appendix 7: Paper presented at the Society of Diary Cattle Veterinarians of the New Zealand Veterinary Association 26th annual conference, Rotorua. Scuffham, A., Firth, E., Stevenson, M., & Legg, S. Musculoskeletal discomfort in New Zealand large animal veterinarians. In: Proceedings of the Society of Dairy Cattle Veterinarians of the New Zealand Veterinary Association 26th annual conference. Ed. T. Parkinson. VetLearn, Palmerston North. 24-27 June 2009, pg 201-204. Appendix 8: Paper presented at the New Zealand Equine Veterinary Association Annual Conference, Taupo. Scuffham, A., Firth, E., Stevenson, M. & Legg, S. Musculoskeletal discomfort in New Zealand equine veterinarians. In: Proceedings of the New Zealand Equine Veterinary Association of the NZVA Annual Conference. Ed. M Leyland. VetLearn, Palmerston North. 24-27 June 2009, pg 163. Appendix 9: Paper presented at the 17th International Ergonomics Association World Congress on Ergonomics, Beijing. Musculoskeletal discomfort in New Zealand (non-clinical) veterinarians. Scuffham, A., Legg, S., Stevenson, M. & Firth, E. (9-14 August, 2009). [CD-ROM] / This thesis comprises three chapters about musculoskeletal discomfort (MSD) in veterinarians. Two of these chapters have been submitted to peer reviewed journals and one is in preparation for submission. The first chapter describes the prevalence and risk factors associated with MSD in New Zealand veterinarians. The second chapter is a paper on the tasks considered by veterinarians to cause MSD. The third chapter is a review of published literature on musculoskeletal problems (MSP) in veterinarians. The first chapter in this thesis describes a cross-sectional study of 867 New Zealand veterinarians. We used a modified Nordic musculoskeletal questionnaire to enquire about the presence or absence of MSD, whether this affected normal activities and if MSD necessitated absenteeism from work. Additional questions enquired about work activities, psychosocial factors and workload. The overall period prevalence of MSD was 96%. Normal activities were affected in 67% and 18% of participants reported that they had been absent from work due to MSD. Factors associated with the presence of MSD requiring time off work for clinical veterinarians included 10 year increases in age (odds ratio (OR) 1.26, 95% CI 1.05 - 1.52), work involving awkward grip and hand movements 100% of time (OR 12.91, 95% CI 3.46 – 84.21) and those who were dissatisfied with the level and difficulty of their work (OR 2.72, 95% CI 1.11 - 6.56). In the second chapter in this thesis, veterinarians were asked to indicate tasks that they considered ‘most likely to lead to musculoskeletal aches and pains’ and ‘why these tasks were likely to be the most risky’. They were also asked to suggest ‘any solutions that they applied or knew of’ to reduce musculoskeletal aches and pains. They identified the following tasks: lifting, surgery, rectal palpations and animal handling. Their reasons were primarily related to physical risk factors. Few identified psychosocial risk factors. The most common suggested solutions involved training and selection strategies rather than redesign of tasks, activities or facilities. These findings are consistent with a participatory ergonomics approach for reducing the risk of MSD, which aims to enhance personal well-being and improved system performance. The third chapter in this thesis - a review of the literature - focuses on the prevalence and nature (discomfort, pain, injury and disorders) of MSP amongst veterinarians. Veterinarians are exposed to a range of physical and psychosocial occupational hazards that have been well documented and associated with MSP. The range of reported prevalence estimates in this review was 50% to 96%. This range may reflect real differences among the veterinary populations studied, or more likely be due to differences in MSP definitions, study methodologies, and response rates. The magnitude of the reported prevalence justifies further research to triangulate data and determine other factors associated with MSD. Most of the studies in the review focused on physical risk factors. The lack of studies into psychosocial risk factors for MSP needs to be addressed.

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