What you've heard
Sync your workouts to your cycle: lift heavy in the first half, go easy in the second
Verdict
Not supported
Not supported. Train consistently and adjust on days you feel bad, whatever the reason.
Should you sync your workouts to your cycle?
Not supported. Train consistently and adjust on days you feel bad, whatever the reason.
The idea turns a real fact, that hormones swing across the cycle, into a training plan. The largest meta-analysis found at most a trivial dip in performance around menstruation, rated the evidence low quality, and concluded that general guidelines "cannot be formed." An umbrella review judged it "premature" to say that hormone swings meaningfully change strength or muscle growth. A small randomized study with hormone-confirmed phases found that muscle built protein at the same rate after lifting in either half of the cycle.9
Where the book tests it
What the book recommends instead
In the reproductive years, track your cycle as a vital sign
ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.for spotting problems earlythe wider vital-sign idea is expert opinionHow: note the first day of each period, how long it lasts and how heavy it is, in any calendar or app, and watch for change from your own pattern. Why: the cycle reports on energy, iron loss, hormones and, later, the start of the transition, for free.
At every stage, lift
StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.for strengthProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.for boneHow: two strength sessions a week of about thirty minutes. The home session in Chapter 4 needs only a chair, a wall and a loaded bag; add load until the last few repetitions feel hard. After fifty, or with low bone mass, work toward heavier lifts and impact training taught in person. Why: bone loss is fastest around the final period, lean mass falls across the transition, and supervised heavy lifting twice a week built spine bone in women with low bone mass, while walking alone does little.
Sources
- 9.McNulty, K.L., Elliott-Sale, K.J., Dolan, E., Swinton, P.A., et al. (2020). "The effects of menstrual cycle phase on exercise performance in eumenorrheic women: a systematic review and meta-analysis." Sports Medicine, 50(10), 1813-1827. https://doi.org/10.1007/s40279-020-01319-3 ; Colenso-Semple, L.M., D'Souza, A.C., Elliott-Sale, K.J., and Phillips, S.M. (2023). "Current evidence shows no influence of women's menstrual cycle phase on acute strength performance or adaptations to resistance exercise training." Frontiers in Sports and Active Living, 5, 1054542. https://doi.org/10.3389/fspor.2023.1054542 ; Colenso-Semple, L.M., McKendry, J., Lim, C., Atherton, P.J., et al. (2025). "Menstrual cycle phase does not influence muscle protein synthesis or whole-body myofibrillar proteolysis in response to resistance exercise." Journal of Physiology, 603(5), 1109-1121. https://doi.org/10.1113/JP287342 (The 2025 crossover trial enrolled 12 women.; McNulty et al. pooled 78 studies)
Note numbers are those of Chapter 15, Women's Bodies Across the Life Course.
This verdict is one of the "What you've heard" boxes in Chapter 15, Women's Bodies Across the Life Course, where the book tests the claims people repeat against the studies behind them.
Educational content, not medical advice. Disclaimer.