Factors related to musculoskeletal disorders in

Background: Musculoskeletal disorders are a major problem in the adult working population and are the most frequently reported cause of workrelated disease in many countries. Police working in active duty are subject to occupation-specific exposures in the workplace which could place them at an increased risk of developing musculoskeletal disorders. These exposures include the requirement to wear a duty belt and body armour as well as sitting for long periods in fleet vehicles. It is well recognised that the development of musculoskeletal disorders is multifactorial and that both physical and psychosocial workplace factors must be considered when addressing this issue. Aim: The overall aim of this thesis was to increase knowledge relating to musculoskeletal disorders in Swedish police by exploring the prevalence of pain and its relationship to physical and psychosocial factors in the work environment. Methods: Studies included in this thesis were conducted using different quantitative methods. Studies I and II were based on data from a selfadministered online survey, distributed to all police officers working in active duty. Descriptive statistics and regression analyses were used to document the prevalence of musculoskeletal pain and the effects of exposure variables (physical and psychosocial) and covariates on multi-site pain. Study III was conducted using a three-dimensional gait analysis system incorporating two force plates to explore the effect of different load carriage systems on kinematic and kinetic variables. These included: a) a standard load carriage condition, incorporating duty belt and body armour, b) an alternate load carriage condition, incorporating thigh holster, load-bearing vest and body armour, and c) a control condition in which no equipment was worn. Study IV included the same three conditions as in Study III but investigated sitting postures and comfort. A pressure mat was utilised to determine contact pressure and contact area while sitting in and driving police vehicles while a survey was used to measure experienced discomfort related to vehicle seat, in vehicle tasks and in specific body regions after driving police fleet vehicles. Non-parametric statistical tests were used to investigate differences between load carriage conditions in Studies III and IV. Results: The results of this thesis revealed that the most frequently reported musculoskeletal disorder among Swedish police working in active duty was lower back pain (43.2%) and that multi-site musculoskeletal pain (41.3%) was twice as prevalent as single-site pain (19.7%). The results from regression analyses showed that both physical and psychosocial workplace factors were associated with an increase in the odds ratio (OR) for multi-site musculoskeletal pain. The physical workplace factor with the greatest association to multi-site musculoskeletal pain was found for individuals reporting discomfort experienced from wearing duty belts (OR 5.42 (95% CI 4.56 – 6.43)). The psychosocial workplace factor with the greatest association to multi-site musculoskeletal pain was found for individuals reporting highstrain jobs (OR 1.84 (95% CI 1.51 – 2.24)). When investigating the effect of different load carriage conditions on gait kinematic and kinetics, it was demonstrated that wearing body armour, or body armour combined with a load-bearing vest, resulted in less rotation of the trunk when compared to not wearing any equipment. It was also found that wearing a thigh holster and load-bearing vest allowed for a greater range of rotation in the right hip compared to the standard load-bearing condition, which incorporated a beltmounted hip holster. Kinetics of the ankle joints were greater for both load carriage conditions compared to the control condition. Discomfort ratings revealed a clear preference for the alternate load-carriage condition incorporating a thigh holster and a load-bearing vest. After driving, the greatest level of discomfort was reported when wearing the duty belt in the standard load carriage condition (36; IQR 14 52 mm). The lower back was found to be the body region with most experienced discomfort (30.5; IQR 11 42 mm). Pressure data demonstrated that wearing a thigh holster and loadbearing vest resulted in less pressure in the lower back when compared to the standard load carriage condition. At the same time, contact pressure in the upper back increased followed by a decrease in contact area. Conclusion: Musculoskeletal pain is a considerable problem among Swedish police with lower back pain being the most frequently reported. Multi-site musculoskeletal pain was found to be more common than single-site pain and both physical and psychosocial factors were associated to multi-site musculoskeletal pain. Of the exposures studied in this thesis, duty belts and high strain jobs were found to have the greatest association to musculoskeletal pain. The use of load-bearing vest and thigh holster were found to affect levels of discomfort especially while driving. Also range of motion in the trunk and right hip was affected by wearing mandatory equipment.