Caffeine gives women a small lifting edge, on wobbly evidence

Caffeine is one of the most studied performance aids in sport, yet most of the evidence comes from men or mixed-sex groups, leaving women to extrapolate. That matters because previous women-only summaries also had a statistical weakness: they treated multiple results from the same trial as independent, which can make findings look more certain than they really are. This review set out to build a women-specific synthesis that models those dependencies properly. The question is simple: does caffeine before resistance exercise actually help women lift?

The authors searched PubMed, Web of Science, Scopus and the Cochrane Library through 26 April 2026 for randomised, placebo-controlled trials giving a defined caffeine dose before resistance exercise to female participants, or to female subgroups that could be extracted separately. Twenty-four studies were included, 23 of them in the quantitative synthesis, contributing 107 effect sizes. Outcomes were grouped into six domains, including maximal strength, muscular endurance and movement speed, and analysed with three-level models designed for clustered results. Risk of bias and certainty of evidence were formally assessed.

Maximal strength showed a small average benefit, a g of 0.17, with low certainty. Muscular endurance showed a larger average effect, a g of 0.54, but the spread across protocols was so wide that reproducibility looks doubtful. Movement speed showed a small estimate, a g of 0.13, resting on only three study clusters and rated very low certainty. Three further domains, functional strength, functional endurance and total load, had too few studies to pool at all. Analyses of caffeine dose, participant age and resistance load found no reliable pattern.

This is the most statistically careful women-specific summary of caffeine and lifting to date, and its message is more cautious than the broader caffeine literature. It confirms a small strength benefit but shows that once dependent results are modelled properly, confidence shrinks and the endurance effect becomes unreliable across protocols. The authors call for future trials to report menstrual cycle phase, hormonal contraceptive use, menopausal status and habitual caffeine intake, all currently patchy. Until then, women-specific dosing guidance remains unsupported by the evidence.

If you are a woman who lifts, this is a reason to think pre-training caffeine probably offers a small edge on maximal strength, and possibly more on muscular endurance in some settings. It is equally a reason to distrust confident, precise dosing claims aimed specifically at women, because the current evidence cannot support them. Responses appear to vary widely between protocols and people, so the average effect may not describe any individual well.