The evidence on menstrual cycle phase and oral contraceptives on exercise performance is mostly low quality and finds mostly trivial effects — individualisation is the only well-supported recommendation
Interpretation
McNulty et al.'s 78-study meta-analysis found the largest mean effect of cycle phase (early vs late follicular) was ES −0.14 — trivial to small — with 42% of studies rated low quality. Elliott-Sale et al.'s OCP meta-analysis (42 studies, 590 participants) found 83% of studies were moderate-to-very-low quality, and any performance effect of OCP use is 'most likely trivial.' Elliott-Sale et al. (2021 methodology paper) explains why: lack of agreed terminology, no gold-standard for cycle-phase determination, and contraceptive heterogeneity make pooling across studies methodologically fragile. Together these papers argue not that cycle phase/OCP don't matter to any individual, but that population-level prescriptions aren't supported by the current evidence.
Practical implication
Don't recommend specific training-intensity modifications by cycle phase as a general prescription — the mean effect doesn't justify it. Recommend self-monitoring and individualisation instead, and be explicit that the evidence base is currently low quality.
Sources
3 sources, independently verified.
Sports Med 50(10):1813–1827. Pooled 78 studies: trivial reduction in early follicular phase (ES −0.06); largest effect early vs late follicular (ES −0.14). Critically, 42% of included studies were rated low quality. Authors recommend an individualised approach rather than standardised phase-based modification of training, because the mean effect is small and variance between individuals is high.
Sports Med 50(10):1785–1812. Pooled 42 OCP studies: 83% moderate/low/very low quality, 17% high; OCP use might give slightly inferior performance versus naturally menstruating women but the likely effect is trivial and inconsistent; no general guidance warranted — performance is broadly consistent across the OCP cycle. Individualisation recommended.
Sports Med 51(5):843–861. Reviews the methodological challenges that cause female-only studies to yield inconsistent results: lack of agreed terminology, no gold standards for cycle-phase determination, contraceptive heterogeneity. Proposes hormonal-profile-based phase definitions. Explains why low evidence quality in the McNulty and Elliott-Sale 2020 meta-analyses is a methods problem, not just a research-volume problem.