Performance and perceptual effects of L-menthol ingestion: A systematic review and meta-analysis with recommendations for future research

Aim: The aim of this review was to determine the effect of L-menthol ingestion on aerobic exercise performance, rating of perceived exertion, thermal sensation, and thermal comfort. Our hypothesis was that L-menthol ingestion would have a small, positive effect on exercise performance, and at least a moderate effect on perceptual measures.Methods: Six databases (PubMed, Web of Science, Scopus, Embase, CINAHL, SPORTDiscus) were searched for any studies that used L-menthol ingestion during aerobic exercise in trained participants. Standardised mean differences (Hedges' g) were calculated and combined using random-effects meta-analysis. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool.Results: Six studies involving 78 athletes (14% female) who ranged from recreationally to highly trained met inclusion criteria. The effect of L-menthol ingestion on exercise performance was inconclusive, with potential future effects ranging from small detrimental (g=–0.21) to medium beneficial (g=0.65). There was evidence that studies with a high risk of bias (2 studies; g=0.49) showed larger effects than those with some concerns (4 studies; g=0.09). The effect of L-menthol on perceptual measures was inconclusive.Conclusion: L-menthol ingestion has the potential to be a low-risk ergogenic strategy that could produce small performance benefits. However, available evidence from six studies with at least some risk of bias concerns does not support its use, and detrimental effects on performance and perception cannot be ruled out. Future studies should include appropriate blinding and control conditions, use standardised L-menthol concentrations, and appropriately consider sample size planning to establish whether L-menthol ingestion has meaningful ergogenic potential.