Background We determined the extent to which heart rate variability (HRV) responses to daily physical activity differ between subjects with and without chronic neck pain.

Method Twenty-nine subjects (13 women) with chronic neck pain and 27 age- and gender-matched healthy controls participated. Physical activity (accelerometry), HRV (heart rate monitor) and spatial location (Global Positioning System (GPS)) were recorded for 74 hours. GPS data were combined with a diary to identify periods of work, and of leisure at home and elsewhere. Time- and frequency-domain HRV indices were calculated, and stratified by period and activity type (lying/sitting, standing, or walking). ANCOVAs with multiple adjustments were used to disclose possible group differences in HRV.

Results The pain group showed a reduced HRV response to physical activity compared with controls (p=.001), according to the sympathetic-baroreceptor HRV index (LF/HF, ratio between low and high frequency power), even after adjustment for leisure time physical activity, work stress, sleep quality, mental health, and aerobic capacity (p=.02). The parasympathetic response to physical activity did not differ between groups.

Conclusions Relying on long-term monitoring of physical behavior and heart rate variability, we found an aberrant sympathetic-baroreceptor response to daily physical activity among subjects with chronic neck pain.