Injury epidemiology in Police Force recruits: a prospective cohort study of a rarely researched population

Introduction: Police Force recruits undergo strenuous physical, operational skills and combat training as a part of their academy qualification program, similarly to military recruits. However, a lack of published epidemiological injury data presents a major challenge to designing prevention programs appropriate for this population. Little to no data exists on injury epidemiology or risk factors. Our objectives were: 1) report the musculoskeletal injury epidemiology in Western Australian (WA) Police Force recruits, 2) determine the influence of age and sex on all injuries, and 3) examine the influence of running-related cardiorespiratory fitness on lower-limb and lumbosacral injury risk. Methods: A cohort study of prospectively collected data from WA Police Force recruits between 2018-2021 was performed. Injury was defined as ‘time-loss’. Injury incidence rate per 1,000 training days (Poisson 95% confidence intervals [95%CI]) and burden (time-loss days per 1,000 training days) were calculated. For each injury region and type, the incidence and burden were calculated. The association between age, sex, and injury occurrence were assessed using logistic regression. The influence of running-related cardiorespiratory fitness (assessed by the beep-test) on lower-limb and lumbosacral injury was also determined using logistic regression. Injury rates were depicted using a Kaplan-Meier curve, separated for sex. Results: A total of 1,316 WA Police Force recruits were included, of whom 264 recruits sustained injuries. Injury prevalence was 20.1% and the incidence rate was 1.74 (95%CI 1.52-1.94) injuries per 1,000 training days. Knee injuries had the highest injury burden (10.43 time-loss days per 1,000 training days) and ligament/ joint injuries accounted for the highest injury burden (13.92 time-loss days per 1,000 training days), however 26.9% of injuries were not-specified by injury type. Most injuries occurred during physical training (31.8%). Being over 30 years old (OR= 1.6, p=0.002) and female sex (OR= 1.8, p<0.001) increased injury risk. 15.2% of recruits (n=180) with complete datasets (10% of all recruits were missing data) sustained a lower-limb or lumbosacral injury. Increased cardiorespiratory fitness decreased lower-limb and lumbosacral injury risk (OR=0.8, p=0.019). Injury rates decreased throughout the six-month recruit training period and females were injured significantly earlier than males (p=0.021). Discussion: Prevention programs targeting ligament/joint injuries to the lower-limb should be prioritised to reduce injury burden. Interventions that can pre-condition Police Force recruits prior to the commencement of their basic training, specifically targeting females and those aged over 30 years, may reduce the injury burden. Injury surveillance protocols should be reviewed to reduce the proportion of missing and uninformative data. Impact and application to the field: These research findings have clear relevance to practice and policy. Our research has led to the WA Police Force funding the development of a new injury and physical performance surveillance system, that our research team will lead. Furthermore, our research has led to a review of the injury prevention procedures within the WA Police Force, with specific attention to female recruits, recruits aged over 30 years and those with poor baseline fitness. Conflict of interest declaration: This research project was funded by the Western Australian Police Force and Mr Allen is an employee of the Western Australian Police Force. The authors declare no other competing interest.