Background

Aberration in autonomous nervous system regulation may play an important role in the development of work related musculoskeletal disorders (MSD). Recent studies indicated that sympathetic activity was increased relative to vagal effects in subjects with MSD, as measured through heart rate variability (HRV). However, the cause of this physiological change is difficult to determine, since several factors influence HRV, almost importantly the pattern of daily physical activity (PA).The aim of this study was to identify possible differences in PA between workers with and without MSD, and assess associations between HRV and PA. Methods: Twenty-six workers with MSD (41 years, 13 females) and twenty-four matched symptom-free controls from an industry in mid-Sweden participated in the study. ECG was monitored by the First Beat system whereas PA was recorded by a tri-axial accelerometer ActivPAL attached to thigh. GPS data were collected to identify the spatial location of the participants

Results

The groups showed similar distributions of total time spent at work, at home and "elsewhere". The lowest PA levels were found at work for both groups. Leisure time PA "elsewhere" was significantly lower among subjects with MSD than among controls. Time domain HRV variables were clearly correlated with PA levels and showed trend differences (0.05<p<0.1) between the MSD and the control group during sedentary and physically active periods.

Conclusions

Workers with MSD showed a different pattern of leisure time PA compared with symptom-free workers. These PA differences may have contributed in explaining the difference in autonomic activity, as measured through HRV, observed between the two groups, and even in previous studies of similar groups.