Exercise-Induced Hypoalgesia in Healthy Individuals and People With Chronic Musculoskeletal Pain: A Systematic Review and Meta-Analysis.

Exercise-induced hypoalgesia (EIH) is a reduction in pain that occurs during or following exercise. Randomized controlled studies published from 1980 to January 2020 that examined experimentally induced pain before and during/following a single bout of exercise in healthy individuals or people with chronic musculoskeletal pain were systematically reviewed. Data were analyzed using random-effects meta-analyses and studies were appraised using the Cochrane Risk of Bias tool and GRADE. Five thousand eight hundred twenty-nine records were screened, with 13 studies ultimately included. In healthy individuals, aerobic exercise caused large EIH (7 studies, 236 participants; g = -.85 [-1.58, -.13]), dynamic resistance exercise caused small EIH (2 studies, 23 participants; g = -.45 [-.69, -.22]), and isometric exercise did not cause EIH (3 studies, 177 participants; g = -.16 [-.36,.05]). In chronic musculoskeletal pain, isometric exercise did not cause EIH (3 studies, 114 participants; g = -.41 [-1.08,.25]); aerobic (0 studies) and dynamic resistance (1 study) exercise were not analyzed. We conclude that, based on small studies with unclear risk of bias, aerobic and dynamic resistance exercise reduce experimental pain in healthy individuals. Further research is needed to determine whether EIH exists for experimental and clinical pain in people with chronic musculoskeletal pain. Registration: PROSPERO ID: CRD42018085886. PERSPECTIVE: Based on low-quality data from small samples, a single bout of aerobic exercise reduces experimental pain in healthy individuals. The evidence is unclear in people with chronic musculoskeletal pain but warrants further investigation due to the limited number of studies in these populations.