Background: 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 related 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 self-administered 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. 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 the vehicle seat. 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 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 high-strain jobs (OR 1.84 (95% CI 1.51 – 2.24)). 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. 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 belt-mounted 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. 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 load-bearing 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 pain site. 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.