The purpose of this study was to investigate the effects of nocebo administration on perceived soreness and exercise performance following unaccustomed resistance exercise. Untrained males were randomly assigned to one of two treatments: (1) control or (2) negative-belief. For the negative-belief group, participants were given a capsule before exercise containing 400 mg of an inert substance (gluten-free cornstarch) and were told the supplement would increase muscle soreness. The control group received no treatment. An algometer and pain scale was used to obtain soreness, and a goniometer was used to measure elbow range of motion (ROM). Participants completed an eccentric bicep curl pyramid with their non-dominant arm. Rate of perceived exertion (RPE) and repetitions were recorded. Then, 48 h after the initial exercise bout, participants repeated all procedures. Perceived soreness, ROM, average RPE, and total repetitions performed were analyzed. Perceived soreness was significantly higher in both control and negative-belief groups 48 h after exercise (p < 0.001; η2 = 0.23). ROM was significantly lower 48 h post in the negative-belief group (p = 0.004; d = 1.83) while no differences existed for controls (p = 0.999; d = 0.16). Average RPE was unaffected between groups (p = 0.282; η2 = 0.07). Total repetitions were significantly lower 48 h post in the negative-belief group (p < 0.001; d = 2.51) while no differences existed for the controls (p = 0.999; d = 0.08). Findings suggest that 48 h after unaccustomed resistance exercise, negative expectation does not worsen soreness but hinders ROM and exercise performance.
Keywords: negative-belief; range of motion; rate of perceived exertion eccentric.