Several studies explored the effects of paracetamol (acetaminophen) ingestion on endurance performance, but their findings are conflicting. Therefore, this review aimed to conduct a meta-analysis examining the effects of paracetamol ingestion on endurance performance. Five databases were searched to find relevant studies. The PEDro checklist was used to assess the methodological quality of the included studies. Data reported in the included studies were pooled in a random-effects meta-analysis. A total of ten studies with good or excellent methodological quality were included in the meta-analysis (pooled n = 141). All included studies had a randomized, double-blind, crossover design. In the main meta-analysis, there was no significant difference between the effects of placebo and paracetamol on endurance performance (Cohen's d = 0.09; 95% confidence interval (CI): -0.04, 0.22; p = 0.172). However, an ergogenic effect was found when we considered only the studies that provided paracetamol 45 to 60 min before exercise (Cohen's d = 0.14; 95% CI: 0.07, 0.21; p < 0.001). In a subgroup analysis that focused on time-to-exhaustion tests, there was a significant ergogenic effect of paracetamol ingestion (Cohen's d = 0.19; 95% CI: 0.06, 0.33; p = 0.006). There was no significant difference between placebo and paracetamol in a subgroup analysis that focused on time trial tests (Cohen's d = 0.05; 95% CI: -0.12, 0.21; p = 0.561). In conclusion, paracetamol ingestion appears to enhance performance (a) in time-to-exhaustion endurance tests and (b) when consumed 45 to 60 min before exercise.
Keywords: aerobic endurance; data synthesis; ergogenic effects.