The influence of acetaminophen on repeated sprint cycling performance.

Introduction: The aim of this study was to investigate the effect of acetaminophen on repeated sprint cycling performance.
Methods: Nine recreationally active male participants completed a graded exercise test, a familiarisation set of Wingate Anaerobic Tests (WAnTs) and two experimental sets of WAnTs (8 × 30 s sprints, 2 min active rest intervals). In the experimental WAnTs, participants ingested either 1.5 g acetaminophen or a placebo in a double-blind, randomised, crossover design. During the WAnT trials, participants provided ratings of perceived pain 20 s into each sprint. Mean and peak power output and heart rate were recorded immediately following each sprint, and percentage decrement in mean power output was subsequently calculated.
Results: Participants cycled at a significantly greater mean power output over the course of 8 WAnTs (p < 0.05) following the ingestion of acetaminophen (391 ± 74 vs. 372 ± 90 W), due to a significantly greater mean power output during sprints 6, 7 and 8 (p < 0.05). Percentage decrements in mean power output were also significantly reduced (p < 0.05) following acetaminophen ingestion (17 ± 14 vs. 24 ± 17 %). No significant differences in peak power output, perceived pain or heart rate were observed between conditions.
Conclusion: Acetaminophen may have improved performance through the reduction of pain for a given work rate, thereby enabling participants to exercise closer to a true physiological limit. These results suggest that exercise may be regulated by pain perception, and that an increased pain tolerance can improve exercise performance.