Conditioned Pain Modulation Predicts Exercise-Induced Hypoalgesia in Healthy Adults

Conditioned pain modulation (CPM) is the idea that pain inhibits pain, and has potential rehabilitation implications for exercise prescription. The objective of this study was to determine if changes in pressure pain perception following a thermal conditioning stimulus (i.e., CPM) was attenuated with aging and whether CPM predicted pain relief following exercise (exercise-induced hypoalgesia, EIH) in healthy young and older adults. Twenty young (21.9 ± 3.3 years, 10 men) and 19 older (72.0 ± 4.5 years, 10 men) adults participated in three sessions: one familiarization and two experimental (EIH and CPM). Pressure pain perception was assessed using a weighted Lucite edge placed on the right index finger for one minute. EIH was determined by measuring pressure pain perception before and after prolonged submaximal isometric contraction of the elbow flexors. CPM was assessed by measuring pressure pain perception at the finger while the foot was immersed in neutral water versus painful ice water. Young, but not older, adults reported a reduced pressure pain at the finger while their foot was immersed in the ice water bath compared with the neutral bath (i.e., CPM; trial x age: P = 0.001). Pressure pain ratings decreased following exercise (P = 0.03) that was perceived as painful (peak arm pain = 7.0 ± 3.3) for both young and older adults. Regression analysis showed that after controlling for age and baseline pain, CPM predicted EIH (model Adjusted R = 0.23, P =0.007).

CPM was attenuated in older adults as measured with a noxious pressure stimulus following a thermal conditioning stimulus, and adults with greater CPM were more likely to report increased EIH.