Frequently asked questions

Hormones change over the cycle, and many women notice differences in energy, mood or appetite. Whether that leads to rules for everyone is another question – and for training, current research says no (see the next question). So for each phase Rhythmus describes what is known, each time with a rating and a source. What keeps coming back for you personally is shown under “Your pattern” in History once enough cycles are logged. The gentler alternative on low-energy days follows your own check-in, not the phase.

On average, hardly. A 2026 randomised trial (D'Souza et al.) compared over three cycles whether it is better to train a lot in the follicular phase and little in the luteal phase: muscle growth and strength increased equally in every version. Another 2026 study (Munteanu et al.) found that cycle phase had little effect on training performance, while motivation on the day did. Reviews that measured hormone levels (Schlie et al. 2025; Britton & Duncan 2026) find small, inconsistent effects in the first days of the period and, in some studies, slightly better coordination around ovulation, with a medium to high risk of bias. That's why Rhythmus gives no training instructions per phase.

Rhythmus uses the widely used calendar method: ovulation is anchored 14 days before the next expected period, because the luteal phase (the time between ovulation and the period) is experientially far more constant across cycles than the time before it. This is the same basis other cycle apps use. Worth knowing: this is a calculation, not a measurement, and it is not suitable for contraception. A long-term study from Heidelberg (Malliou-Becher et al. 2026, 1,051 women over twelve cycles each) found that within a year, ovulation shifted by a week or more in over half of the women, and by at least four days in 96%. The more of your own period data you enter, the better the calculation fits your history – but it can never be more precise than that natural variation. With hormonal contraception, an irregular cycle or during perimenopause, the prediction is inherently less reliable.

From the Mifflin-St Jeor equation — one of the best-studied estimation formulas for basal metabolic rate, and on average the most accurate in validation studies of healthy adults. The basal rate is scaled by your activity factor (from training days and intensity) and adjusted slightly according to your target weight. Like every formula this is an estimate, not a measurement — with pronounced over- or underweight or particular health conditions, the deviation can be larger.

Because protein is the nutrient where "just watch the calories" most easily falls short. Since version 1.6, Rhythmus uses the reference values of the German Nutrition Society (DGE): 0.8 g per kilogram of body weight, 1.0 g from age 65; with a BMI above 25, it uses the weight that corresponds to a BMI of 25. According to the DGE, recreational exercise doesn't require a higher intake. For regular strength training, the ISSN sports nutrition society puts the need at 1.4 to 2.0 g per kg – that range is shown as a note under the target. Previously Rhythmus used values for competitive athletes (1.7–2.0 g/kg) as the target for everyone. Carbohydrates and fat are not prescribed separately; the recipe ideas are scaled to your calorie target.

The selection follows the Blueprint protocol by Bryan Johnson — the original founding idea behind Rhythmus — and carries its approach of longevity-oriented supplementation into this app. Rhythmus names no brand, links to no retailer and sells nothing; all you see are active ingredients and amounts. Only what you adopt yourself ends up on your list. Which preparation you take, and where you buy it, is your decision. The amounts are not independently lab-tested — always check the label of your own product before taking anything.

No. All information on training, nutrition, calorie and protein targets and supplements is general orientation based on publicly available research — not individual medical, dietary or sports-science advice. With existing conditions, pregnancy, plans to conceive, menopausal symptoms, or before taking new supplements, always discuss it with a doctor, ideally with blood work.

Your data is private and visible only to you — there is no tracking and no analytics software. Details are in the privacy policy.

Yes, entirely. Rhythmus is a non-commercial passion project with no payment model and no advertising.