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rhythmus Open app
Knowledge

What we've changed – and why

When new studies or our own checks show that something in Rhythmus isn't right, we change it and note it here: what it was before, what applies now and why.

Also in: Deutsch · Español

28 September 2026 · Version 1.6.0

No more training instructions by cycle phase

Before
The phase texts recommended what to train in which half of the cycle, for example heavier in the first half.
Now
Each phase now shows what research knows, with a rating and a source. Your weekly plan stays as you set it; your daily check-in does the steering.
Why
A 2026 randomised trial tested phase-based training directly: every variant gained the same. A 2025 review found strength largely unchanged across the cycle, and another 2026 study found motivation on the day mattered more than the phase.

More on this: Cycle-based training: what is really supported by evidence

Sources (3)
  1. D'Souza, A. C., Van Every, D. W., Bhinder, A. et al. (2026): Menstrual Cycle Phase Does Not Influence Training-Induced Muscle Hypertrophy or Strength: A Randomized Controlled Trial. Medicine & Science in Sports & Exercise 58(10), 2255–2273. View source
  2. Schlie, J., Krassowski, V. & Schmidt, A. (2025): Effects of menstrual cycle phases on athletic performance and related physiological outcomes: a systematic review of studies using high methodological standards. Journal of Applied Physiology 139(3), 650–667. View source
  3. Munteanu, G., Halson, S. L., Huynh, M. et al. (2026): The Effect of Menstrual Cycle Phase, Symptoms, Motivation, and Readiness to Perform on Resistance Training Performance. Sports Medicine 56(9), 2325–2339. View source

28 September 2026 · Version 1.6.0

Protein target from the DGE instead of 1.7 to 2.0 g for everyone

Before
The app set a protein target of 1.7 to 2.0 g per kilogram of body weight for everyone.
Now
The target follows the German Nutrition Society's reference values: 0.8 g per kilogram, 1.0 g from age 65. The ISSN range of 1.4 to 2.0 g is shown alongside as a note for anyone who strength-trains regularly.
Why
According to the ISSN, the higher range applies to people who train, and its evidence base in women is thin: most of the studies were done with men. So it didn't hold up as a target for everyone.

More on this: How much protein do you need if you train?

Sources (3)
  1. German Nutrition Society (DGE) (reference values, 2017): Referenzwerte für die Nährstoffzufuhr: Protein. DGE. View source
  2. Jäger, R. et al. (2017): International Society of Sports Nutrition Position Stand: Protein and Exercise. Journal of the International Society of Sports Nutrition 14, 20. View source
  3. Sims, S. T., Kerksick, C. M., Smith-Ryan, A. E. et al. (2023): International Society of Sports Nutrition Position Stand: Nutritional Concerns of the Female Athlete. Journal of the International Society of Sports Nutrition 20(1). View source

28 September 2026 · Version 1.6.0

Life stages: recommendations brought in line with the sources

Before
Among other things, they said strength training four times a week, 1,200 to 1,500 mg of calcium, and 300 extra kcal in pregnancy from the second trimester.
Now
The texts now reflect what the WHO and the German Nutrition Society say: strength training on two or more days, 1,000 mg of calcium, and in pregnancy about 250 extra kcal in the second and 500 in the third trimester.
Why
The old numbers couldn't be traced to any current recommendation. Going through sentence by sentence, we replaced them with the values these bodies actually give.
Sources (3)
  1. Bull, F. C., Al-Ansari, S. S., Biddle, S. et al. (2020): World Health Organization 2020 guidelines on physical activity and sedentary behaviour. British Journal of Sports Medicine 54(24), 1451–1462. View source
  2. German Nutrition Society (DGE) (reference values, 2013): Referenzwerte für die Nährstoffzufuhr: Calcium. DGE. View source
  3. German Nutrition Society (DGE) (reference values, 2015): Referenzwerte für die Nährstoffzufuhr: Energie. DGE. View source

28 September 2026 · Version 1.6.0

“Your pattern” replaces “What stands out”

Before
The app reported the phase with the lowest energy and symptoms that clustered in a phase after only a few days.
Now
“Your pattern” only reports what recurs at the same point in your cycle, corrects for weekdays and has to be confirmed twice in a row.
Why
In our own simulation, the old approach invented a pattern for 84 to 91 % of users, even with no real link. The ISSN advises female athletes to watch their own patterns, but then the analysis has to be able to tell chance from signal.

More on this: Cycle-based training: what is really supported by evidence

Sources (1)
  1. Sims, S. T., Kerksick, C. M., Smith-Ryan, A. E. et al. (2023): International Society of Sports Nutrition Position Stand: Nutritional Concerns of the Female Athlete. Journal of the International Society of Sports Nutrition 20(1). View source

24 September 2026 · Version 1.5.5

Supplements: nothing pre-filled and nothing by cycle phase

Before
The supplement list came pre-filled, and the app suggested intake by cycle phase.
Now
Your list only contains what you add yourself. Nothing follows the cycle phase, and iron comes with the note to have your ferritin checked first.
Why
We found no evidence for timing supplements by cycle phase. And some things don't belong on a daily list unasked: too much iron isn't harmless, and St John's wort can weaken hormonal contraception.
Sources (1)
  1. National Institutes of Health, Office of Dietary Supplements: Iron — Fact Sheet for Health Professionals. NIH ODS. View source

22 September 2026 · Version 1.5.2

Iron: ferritin, not just a blood count

Before
On iron, the app pointed to a blood count.
Now
The app now names the ferritin value explicitly, in all three languages.
Why
Normal haemoglobin doesn't rule out empty iron stores; it only drops late. In female athletes, endurance performance was already worse at low ferritin.

More on this: Iron, periods and exercise: test first, then supplement

Sources (2)
  1. Pasricha, S.-R., Tye-Din, J., Muckenthaler, M. U. & Swinkels, D. W. (2021): Iron deficiency. The Lancet 397(10270), 233–248. View source
  2. Pengelly, M., Pumpa, K., Pyne, D. B. & Etxebarria, N. (2025): Iron deficiency, supplementation, and sports performance in female athletes: A systematic review. Journal of Sport and Health Science 14, 101009. View source

8 September 2026 · never released

“Training by cycle phase” analysis built and removed again

Before
The plan was an analysis of the phase in which you train most often.
Now
It doesn't exist. We took it out again the same day.
Why
Our check showed that with a cycle of exactly 28 days, each phase always falls on the same weekdays. With a fixed weekly plan, the analysis would have reported a pattern that is purely the calendar, and more data would only have entrenched the error.

The reason was our own check.

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