A smaller magnitude of exercise-induced hypoalgesia in African Americans compared to non-Hispanic Whites: A potential influence of physical activity.

This study compared exercise-induced hypoalgesia (EIH) between African Americans (AAs, n=16) and non-Hispanic Whites (NHWs, n=16), and examined the potential influence of physical activity (PA) on the racial/ethnic difference in EIH. The PA levels were quantified using a questionnaire, and intensity of electrical stimulus to produce moderate pain was individually determined. Participants squeezed a hand dynamometer at 25% of their maximal strength for three minutes, followed by a three-minute post-exercise rest. Numeric ratings to electrical stimulus at the pre-determined intensity were recorded every one minute during and after exercise. Compared to NHWs, AAs reported less lifestyle PA. Both AAs and NHWs showed EIH, but AAs exhibited a smaller magnitude of EIH than NHWs. However, this difference in EIH disappeared after controlling for the lifestyle PA levels. The results suggest that AAs exhibit less efficient pain modulation than NHWs, and AAs' reduced PA could potentially explain the observed difference in EIH.