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Cycles & seasons · 3 min read
Training with your cycle: what the evidence supports
Phase-based training plans promise a lot. The largest meta-analysis found trivial average performance differences across the cycle, on low-quality evidence. Here is what holds up, what is oversold, and how to use your own data instead of a textbook calendar.
Four phases, one moving target
A textbook cycle runs 28 days: menstruation, the follicular phase, ovulation around day 14, then the luteal phase. Real cycles run 21–35 days, and most of that variation sits in the follicular phase. Ovulation can drift by four days or more from the textbook date — cycle to cycle, in the same person. The diagram is an average, and averages do not menstruate.
Most phase-based training advice is really calendar advice. It assumes your ovulation lands on day 14 and your phases match the picture. Without ovulation testing, a calendar can only guess which phase you are in on any given day. A guess about your hormones is a weak foundation for a training prescription, however confident the plan looks.
What the evidence supports
The largest meta-analysis on this question (McNulty et al., 2020) pooled 78 studies and found a trivial average reduction in performance during the early follicular phase — and rated the underlying evidence quality low. Trivial means smaller than day-to-day noise. On average, knowing your phase tells you little about what you can lift today or how fast you can run.
What is well established is quieter. In the luteal phase, core temperature runs roughly 0.3–0.5 °C higher, resting heart rate tends to rise, and heart-rate variability tends to fall. The same session can feel harder at the same output. Symptoms — cramps, disrupted sleep, low energy — are real and can affect training. A trivial average does not make your Tuesday feel trivial.
What is oversold
"Lift heavy in the follicular phase for extra gains" traces back to a handful of small studies, some with fewer than 20 participants, and it has not replicated at scale. Reviewers consistently flag the field's methodology — small samples, poor phase verification (Elliott-Sale et al., 2021). Building a whole periodisation model on those studies is building on sand.
The trivial average cuts the other way too: it cannot tell you about you. A meta-analysis describes populations. Some individuals report consistent, meaningful phase effects; others report none at all. The honest position is that the calendar predicts little, your symptoms predict more, and only your own logged data can say which group you belong to.
Use your data, not a diagram
Track your cycle alongside training and recovery data for at least three cycles. Look for repeating patterns: does resting heart rate climb in your luteal phase? Does the same session cost more effort in week four than week two? If a pattern repeats across cycles, act on it — shift hard sessions by a few days, not by philosophy.
Keep the structure of training intact. Progressive overload works in every phase, and no phase requires you to drop intensity by default. One caution outranks all of this: if your cycle becomes irregular or stops while training hard, that can signal low energy availability. It is a health question before it is a training question — speak to a clinician.
Train with your cycle, honestly
Dates, symptoms, and how sessions felt. One cycle is an anecdote; three is the start of a pattern.
Resting heart rate and HRV shift in the luteal phase for many people. Check whether yours actually do.
If hard sessions repeatedly cost more in one week, move them a few days. Keep the overall load.
Cycles that stop under heavy training suggest low energy availability. That is a clinician conversation, not a training tweak.
Quick answers
Should I only lift heavy in the follicular phase?
No. That claim comes from a few small studies that have not replicated at scale, and the largest meta-analysis found trivial average performance differences across phases. Keep progressive overload running all month. Shift individual hard days when your own logged data — not the calendar — says a session will cost too much.
Why does training feel harder before my period?
In the luteal phase, core temperature runs about 0.3–0.5 °C higher, resting heart rate tends to rise, and sleep is often worse. The same session can feel harder at the same output. That is a normal, well-documented shift. It is about effort and comfort, not a collapse in capability.
What if my cycle is irregular or has stopped?
Calendar-based advice assumes regularity, so it applies even less to you. Track symptoms rather than predicted phases. If your period becomes irregular or stops during hard training, that can signal low energy availability and is worth raising with a clinician. It is a health question before it is a training question.
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