Train & Fuel With Your Cycle
Stacy Sims says use your own cycle data, not rigid syncing rules the evidence doesn't support, to time hard training and fueling. Track your cycle for 2 to 3 months to find your pattern; low-hormone days through ovulation often handle heavy work best, and Sims is blunt that under-fueling, not hard training, is the real threat to a healthy cycle.
Log your cycle and training for 2 to 3 months Note cycle day, session quality, perceived effort, sleep and mood; a wearable or a simple journal both work
Your own pattern is far more reliable than population studies, which Sims considers too weak to prescribe from.
Schedule your hardest work day 1 through ovulation Heavy lifting, sprints and high-intensity sessions in the follicular phase when you tend to tolerate stress and access carbs well
Lower hormones generally mean better stress resilience, recovery and intensity; many women feel strongest here.
Keep training, but fuel and recover more Slightly more protein and carbohydrate around sessions; allow more recovery; dial back only if you feel you need to
Higher progesterone raises core temperature, sympathetic drive and inflammation and reduces carb access, so the same load costs more.
Let how you feel set the intensity, not a chart If you feel good, train hard regardless of cycle day; if flat, adjust
Sims calls subjective readiness the most reliable signal; rigid phase rules ignore individual variation.
Do not train fasted and refuel after ~15g protein pre-session, protein plus carbs within 30 to 45 min after; never run a chronic energy deficit
Under-fuelling, not intensity, is what disrupts cycles and stalls progress; this is her central warning.
Address low ferritin deliberately, not by default If a blood test shows low ferritin, Sims suggests iron every other day for about 10 days starting on day 1 of the cycle; do not blanket-supplement iron
Iron status affects training, but unnecessary iron is harmful; test before supplementing.
Move toward heavy, lower-rep lifting As estrogen flux ends, prioritise heavy resistance work (about 2 to 3 reps in reserve) over chasing the cycle
Estrogen is a key driver of strength; once it falls, heavy load matters more than cycle timing.
Estrogen and progesterone shift carbohydrate access, core temperature, inflammation and stress tolerance across the cycle, which is why a session can feel very different week to week.
View sources
Should Women Train According to the Menstrual Cycle? What the research really says (Dr. Stacy Sims)
Dr. Stacy Sims AMA: Training and Menstrual Cycles (WHOOP)
Menstrual-cycle periodized training: evidence is still premature (IMPACT study protocol, review of the field)
Not medical advice. This page is for education only and is not a substitute for professional medical care. Consult a qualified clinician before changing your health routine.
Independent curation. YourProtocol is an independent platform. This protocol is based on the publicly available work of Stacy Sims and is not created, reviewed, endorsed by, or affiliated with Stacy Sims or Author, ROAR & Next Level.
Is this for you
- Active women with a regular cycle
- Athletes who want to time hard blocks
- Anyone confused by cycle-syncing trends
- Women approaching perimenopause
Cautions
- Sims is clear the population evidence for strict cycle-syncing is weak; treat phase tendencies as starting points and trust your own tracked data
- The biggest risk is under-fuelling (low energy availability / RED-S), which harms cycles, bone and performance; this protocol is about fuelling enough, not restricting
- Irregular or absent periods, very heavy bleeding, or suspected PCOS: see a doctor rather than self-managing
- Do not supplement iron without a blood test showing you need it
- Hormonal contraception changes these patterns; this is education, not medical advice
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