Endogenous Pain Inhibitory Function: Endurance-Trained Athletes vs Active Controls

Abstract

Objective: Athletes are at risk for developing chronic pain conditions, but the role of exercise in the modulation of pain in athletes has not been well established. The aim of this study was to investigate conditioned pain modulation (CPM) and exercise-induced hypoalgesia (EIH) responses between 13 endurance-trained athletes and 13 normally active controls. Methods: In a cross-sectional, nonrandomized study with two independent groups of college-aged males and females, pressure pain thresholds (PPTs) were assessed in the vastus lateralis (VL) and brachioradialis (BR) using a pressure algometer before and after a conditioning stimulus, an isometric hand grip exercise to failure, and a 30-minute run. Results: PPTs increased following the conditioning stimulus, indicating a CPM response, to a similar degree in the BR (19.3% ± 26.5% vs 18.6% ± 16.2%, P = 0.93) and VL (18.9% ± 25.9% vs 28.7% ± 27.4%, P = 0.73) in the athletes and controls. PPTs increased following isometric exercise to a similar extent in athletes and controls in the BR (23.9% ± 22.8% vs 28.2% ± 24.0%, P = 0.75) and VL (15.8% ± 14.8% vs 15.5% ± 11.6%, P = 0.94). Following 30 minutes of running, EIH was similar between athletes and controls in the VL (21.2% ± 17.2% vs 13.8% ± 13.3%, P = 0.23) but was attenuated in the BR of the athletes (6.1% ± 16.9% vs 20.9% ± 20%, P = 0.047). Conclusions: Athletes and controls exhibited similar endogenous pain inhibitory function both locally and systemically following CPM and isometric, upper body exercise. After the 30-minute run, BR EIH was reduced in the athletes compared with controls, suggesting a reduced systemic response following familiar exercise - perhaps due to the exercise being perceived as less painful and/or effortful.