Menstrual cycle and training: what the data shows
Many female athletes notice that the same session feels different depending on the day of their cycle. Research confirms fluctuations in recovery values but finds only small and highly individual differences in performance.
What changes measurably
In the second half of the cycle (luteal phase), heart rate variability is on average somewhat lower than in the first half, especially in the days before the period. Resting heart rate and body temperature are often slightly higher. This is a normal part of the cycle and not a sign of poor recovery.
What it means for performance
A large analysis of many studies found that performance may be marginally lower on average during the first days of the period. The effect is very small and the evidence inconsistent. General rules such as "only easy sessions in phase X" cannot be derived from it. The recommendation is to pay attention to your own response.
How to train with it
- Observe over a few cycles on which days sessions feel harder. Wellbeing in ZonePit helps with that.
- If you feel clearly worse on individual days, you may move a hard session. That is a decision by feel, not a rule.
- Severe symptoms, very irregular or missing periods should be checked by a doctor, especially with high training volume.
In ZonePit
If you turn on the cycle feature, ZonePit estimates your phase from the data in Apple Health. In the luteal phase, a slightly higher resting heart rate and lower HRV are not counted as poor recovery. Everything stays on your device, and you can turn the feature off at any time.
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Sources
- Katja M. Schmalenberger et al. (2019): A Systematic Review and Meta-Analysis of Within-Person Changes in Cardiac Vagal Activity across the Menstrual Cycle, Journal of Clinical Medicine 8(11), 1946.
- Kelly Lee McNulty 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.
ZonePit is a training and wellness app, not a medical device.