Self-reported physical activity predicts pain inhibitory and facilitatory function.

UNLABELLED: Considerable evidence suggests regular physical activity can reduce chronic pain symptoms. The dysfunction of endogenous facilitatory and inhibitory systems has been implicated in multiple chronic pain conditions. However, few studies have investigated the relationship between levels of physical activity and descending pain modulatory function.
PURPOSE: The purpose of this study was to determine whether self-reported levels of physical activity in healthy adults predicted 1) pain sensitivity to heat and cold stimuli, 2) pain facilitatory function as tested by temporal summation (TS) of pain, and 3) pain inhibitory function as tested by conditioned pain modulation (CPM) and offset analgesia.
METHODS: Forty-eight healthy adults (age range = 18-76 yr) completed the International Physical Activity Questionnaire (IPAQ) and the following pain tests: heat pain thresholds, heat pain suprathresholds, cold pressor pain, TS of heat pain, CPM, and offset analgesia. The IPAQ measured levels of walking, moderate, vigorous, and total physical activity over the past 7 d. Hierarchical linear regressions were conducted to determine the relationship between each pain test and self-reported levels of physical activity while controlling for age, sex, and psychological variables.
RESULTS: Self-reported total and vigorous physical activity predicted TS and CPM (P < 0.05). Individuals who self-reported more vigorous and total physical activity exhibited reduced TS of pain and greater CPM. The IPAQ measures did not predict any of the other pain measures.
CONCLUSIONS: These results suggest that healthy older and younger adults who self-report greater levels of vigorous and total physical activity exhibit enhanced descending pain modulatory function. Improved descending pain modulation may be a mechanism through which exercise reduces or prevents chronic pain symptoms.