Podcast episode 74 (in German)
Cycle & biohacking: the female rhythm fact-checked
September 12, 2026
The menstrual cycle is the most underrated dashboard in biohacking and at the same time the biggest data gap in sports science. This episode sorts out what the hormonal waves really do to training, sleep and metabolism, and where the app templates exaggerate.
What it is about
The episode starts with physiology: in the follicular phase, oestrogen rises until ovulation; in the luteal phase, progesterone takes over, measurably raises core body temperature and typically depresses nightly heart rate variability. Anyone who does not read their wearable data in relation to the cycle will read a stress slump into it every month that is simply the hormonal situation. Then the episode checks the big sales promise of cycle-based training against the body of studies and finds considerably less there than the apps claim. Better supported are three unspectacular points: the higher energy expenditure in the second half of the cycle, iron requirements and poorer sleep around menstruation. Added to this is how thin the data basis for women is overall.
Key points
- Progesterone raises core body temperature in the luteal phase by about 0.3 to 0.5 degrees — which is why the cycle phase becomes visible in wearable data at all.
- The much-cited 2020 meta-analysis evaluated over 70 studies and found at most trivial performance differences across the cycle phases, with low study quality overall.
- Depending on the study, basal metabolic rate is 100 to 300 kilocalories higher in the luteal phase — the cravings before the period have a measurable basis.
- In the US, it was only a 1993 law that made the inclusion of women of childbearing age in clinical studies mandatory.
- In the major sports science journals, women still make up only around one third of study participants; studies with clean cycle control are a small minority.
- Up to three quarters of all women experience premenstrual symptoms, and an estimated 3 to 8 percent have the severe form PMDD, a recognized diagnosis.
- Instead of the app template, the end point is your own pattern over 3 to 4 cycles: energy, sleep, mood and training noted down, ideally supplemented by temperature and HRV.
Where the data stop
The honest limit of this episode is the body of data itself. Cycle-based training plans cannot be derived from the existing research: the differences between phases are small, study quality is low, and the researchers themselves recommend an individual rather than a template-based approach. The same pattern applies to fasting, cold and sauna — the protocols come predominantly from studies in men, and whether women need different ones is only just being discussed.
Under hormonal contraception the basis disappears entirely: the hormonal waves described are then largely switched off, temperature and HRV patterns look different, and cycle-based training simply makes no sense. For seed cycling and expensive cycle supplement bundles there is practically no robust evidence. And two things explicitly do not belong in an optimization programme: an absent cycle is a warning sign, and PMDD needs treatment.
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Published on September 12, 2026.
The topic in the database
- Track cycle phases via temperature, resting heart rate, HRV and mood – and align training, nutrition and sleep with your own pattern rather than app templates.Cycle Tracking & Cycle-Based Training
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-09.