Should training follow the cycle phase?

You may have seen advice to plan your workouts around your cycle: hard training in one half, easier in the other. Here is what the research says, what one of the best-known experts says now, and what you can do with it.

What the research says

• A review of 78 studies found that exercise performance might be slightly lower in the early follicular phase, the first days of your cycle, than in other phases. The difference was trivial, and the quality of the evidence was low. The authors concluded that general guidelines can't be formed and recommended a personalized approach.¹
• For strength training, a review of the reviews found highly variable results and called it premature to conclude that short-term hormone changes across the cycle meaningfully change strength or muscle gains.² A 2025 study of 12 women measured muscle building after lifting in the late follicular phase and the mid-luteal phase and found no difference.³
• Not every researcher agrees. A Danish group argues that lifting in the follicular phase may be better for strength and muscle, and a 2023 review describes how estrogen and progesterone may affect muscle.^4,5 Those are reviews of studies of mixed quality, and the 2025 study above didn't find that difference.

The evidence doesn't show a phase that is best for everyone.

Myth: You should plan your training by cycle phase: hard in the first half, easy in the second.

This has been popular in fitness for years, and it came from a good place: it finally took women's bodies seriously. If you've been training this way, there's nothing wrong with that, and if it works for you, keep going. Reviews of the research don't support it as a rule for everyone,^1,2 and Dr. Stacy Sims, one of the first people to promote it, has updated her own advice.⁶

What Dr. Sims says now

Dr. Stacy Sims is a researcher and one of the best-known voices on women's training. She says she was one of the first to talk about training by cycle phase, about 7 to 8 years ago. In October 2025 she wrote that she has moved on from "train by your phase."⁶

Why she changed her view:

• Hormones vary from person to person, and stress, sleep, illness, travel and contraception can all shift them.
• Studies report averages, and averages hide the range of real responses.
• Performance depends on much more than hormones.
• Not every cycle includes ovulation, especially in people who train hard or aren't eating enough, so a calendar plan can be wrong about where you are in your cycle.⁶

Her current advice:⁶

• Train by readiness, not the calendar. If your energy, sleep and heart rate variability (HRV) look good, go for it. If not, lower the intensity or focus on technique and recovery.
• Lift consistently all month. Don't limit strength training to the first half of your cycle.
• Fuel your workouts every day.
• Keep a simple log of energy, sleep and mood for about three cycles and look for your own repeatable pattern.

Earlier, in 2024, she described a phase pattern: harder training from the first day of your cycle through ovulation, steadier work and more fueling in the luteal phase. She also said you can set a personal best in any phase.⁷ Some of her reasoning, like needing about 12% more protein in the luteal phase, is her own estimate that we couldn't trace to a study we could read, so it needs more research.⁸ A review of the science does say progesterone increases protein breakdown in the luteal phase, but the mechanisms aren't known.⁵

Why a workout can feel different

Even when performance holds steady, effort can feel different:

• After ovulation, body temperature runs higher. A higher resting temperature is reported to make exercise feel harder, especially in hot or humid weather.⁹
• Cramps, tiredness, mood changes and poor sleep can all change your motivation (see the last two lessons).

A workout feeling harder is real, even when your results don't change.