Aerobic Exercise Reduces Pressure More Than Heat Pain Sensitivity in Healthy Adults

Abstract

Objectives: The hypoalgesic effects of exercise are well described, but there are conflicting findings for different modalities of pain; in particular for mechanical vs thermal noxious stimuli, which are the most commonly used in studies of exercise-induced hypoalgesia. The aims of this study were 1) to investigate the effect of aerobic exercise on pressure and heat pain thresholds that were well equated with regard to their temporal and spatial profile and 2) to identify whether changes in the excitability of nociceptive pathways - measured using laser-evoked potentials - accompany exercise-induced hypoalgesia. Subjects: Sixteen healthy adults recruited from the University of New South Wales. Methods: Pressure and heat pain thresholds and pain ratings to laser stimulation and laser-evoked potentials were measured before and after aerobic cycling exercise and an equivalent period of light activity. Results: Pressure pain thresholds increased substantially after exercise (rectus femoris: 29.6%, d = 0.82, P < 0.001; tibialis anterior: 26.9%, d = 0.61, P < 0.001), whereas heat pain thresholds did not (tibialis anterior: 4.2%, d = 0.30, P = 0.27; foot: 0.44%, d = 0.02, P = 1). Laser-evoked potentials and laser heat pain ratings also changed minimally after exercise (d = -0.59 to 0.3, P > 0.06). Conclusions: This is the first investigation to compare the effects of exercise on pressure and heat pain using the same stimulation site and pattern. The results show that aerobic exercise reduces mechanical pain sensitivity more than thermal pain sensitivity.