Associations of different types of physical activity (PA) with musculoskeletal disorders (MSDs) at nine body sites in firefighters

Background: Musculoskeletal disorders (MSDs) are one of the global health and economic burdens. They have a high prevalence in occupational populations such as firefighters. Besides poor postures and sedentary work, inappropriate physical activity (PA) is recognized as a relevant risk factor for MSDs. However, the independent associations between different types of PA and MSDs have not been fully investigated. Objective: We systematically investigated the associations of occupational physical activity (OPA), leisure-time physical activity (LTPA) and transport-related physical activity (TPA) with the onset, pain intensity and frequency of MSDs at nine body sites. We quantified their differential effects, so as to provide scientific evidence for the precise prevention and control of MSDs in high-workload occupational populations. Methods: Multiple linear regression, logistic regression and polynomial regression were applied to analyze the distinct effects of different types of PA (OPA, LTPA, TPA) on the onset, intensity, frequency and cumulative number of painful sites of MSDs at nine body sites. In the state of high-intensity OPA, it was associated with the exacerbated accumulation of MSDs at multiple body sites. Conclusion: High OPA was a key risk factor for MSDs, and high LTPA was a risk factor for MSDs at specific body sites.