Changes in physical activity and heart rate variability in chronic neck-shoulder pain: monitoring during work and leisure time

Neck-shoulder pain (NSP) is a common work-related musculoskeletal disorder with unclear mechanisms. Changes in physical activity and autonomic nervous system regulation may be involved in the pathogenesis of chronic NSP. The aim of the current study was to investigate autonomic regulation in relation to physical activity and perceived symptoms during work and leisure time among workers with chronic NSP (n = 29) as compared to a healthy control group (CON, n = 27). Physical activity was objectively monitored for 7 days using accelerometry. Beat-to-beat heart rate was collected continuously for 72 h, with simultaneous momentary ratings of pain, stress, and fatigue. Duration of sitting/lying, standing and walking, number of steps, and energy expenditure were used as measures of physical activity. Heart rate variability (HRV) indices were extracted in time and frequency domains as reflecting autonomic regulation. Data were divided into work hours, leisure time, and sleep. The NSP group rated higher levels of stress and fatigue at work and leisure, and reduced sleep quality as compared to CON. Elevated heart rate and reduced HRV were found in NSP compared with CON, especially during sleep. The NSP group demonstrated a different pattern of physical activity than CON, with a lower activity level in leisure time. Higher physical activity was associated with increased HRV in both groups. Changes in HRV reflected an autonomic imbalance in workers with chronic musculoskeletal pain. This can be explained by reduced physical activity in leisure time. Intervention studies aimed at increasing physical activity may shed further light on the association between autonomic regulation and physical activity in work-related NSP.