Myth check: cycle, training, women's health
31 claims you hear a lot, checked against the studies and guidelines our articles are built on. Where there's more to say, it's in the linked article.
“True” and “False” mean the sources clearly support or contradict the claim. “Partly”: there's something to it, but the claim goes further. “Not supported”: the studies don't show the claimed benefit.
“Training by cycle phase builds more muscle.”
A randomised trial from 2026 tested exactly this. Every trained variant gained the same amount of muscle and strength, whether most of the volume fell in the first or the second half of the cycle. What mattered was the total amount of training.
More on this: Cycle-based training: what is really supported by evidence
Sources (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
“You're stronger in the first half of your cycle.”
A 2025 review that only included studies with measured hormone levels found maximal and explosive strength largely unchanged across the cycle. A 2026 study saw only minimal differences by phase. How motivated the women felt on the day mattered much more.
More on this: Cycle-based training: what is really supported by evidence
Sources (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
- 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
“You shouldn't exercise during your period.”
The studies give no reason not to. Maximal and explosive strength stay largely the same on bleeding days, and a 2026 meta-analysis found no significant difference in maximal oxygen uptake. Taking it easier on a day with cramps is still a fine choice. It's a decision about the day, not about the cycle.
More on this: Training during your period: what works and what you can adjust
Sources (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
- Britton, I. I. & Duncan, W. C. (2026): The effects of hormone changes over the menstrual cycle on elite athlete performance: meta-analysis and suggested standardised protocol. Reproduction and Fertility 7(3), RAF250131. View source
“Ovulation happens on day 14.”
That assumes a fixed 28-day cycle, and even then it only holds for some women. Large amounts of tracking data show a wide spread, both between people and within the same person. A better estimate counts back from the start of the next period, because the second half of the cycle is more stable than the first.
More on this: How long is a normal cycle – and when is ovulation?
Sources (2)
- Sohda, S., Suzuki, K. & Igari, I. (2017): Relationship Between the Menstrual Cycle and Timing of Ovulation Revealed by New Protocols: Analysis of Data from a Self-Tracking Health App. Journal of Medical Internet Research 19(11), e391. View source
- Cleveland Clinic: Luteal Phase of the Menstrual Cycle: Symptoms & Length. Cleveland Clinic — Health Library. View source
“A normal cycle is 28 days long.”
Cycles of roughly 21 to 35 days count as normal. Length also varies from month to month in the same person; that's the rule, not the exception. 26 days one month and 31 the next is not a finding.
More on this: How long is a normal cycle – and when is ovulation?
Sources (2)
- American College of Obstetricians and Gynecologists: The Menstrual Cycle: Menstruation, Ovulation, and How Pregnancy Occurs. ACOG. View source
- Sohda, S., Suzuki, K. & Igari, I. (2017): Relationship Between the Menstrual Cycle and Timing of Ovulation Revealed by New Protocols: Analysis of Data from a Self-Tracking Health App. Journal of Medical Internet Research 19(11), e391. View source
“The second half of the cycle always lasts 14 days.”
About fourteen days is typical; Cleveland Clinic gives a normal range of roughly ten to seventeen. It does vary much less than the first half, though. That's why cycle apps count ovulation back from the next period.
More on this: The luteal phase: the two weeks before your period
Sources (1)
- Cleveland Clinic: Luteal Phase of the Menstrual Cycle: Symptoms & Length. Cleveland Clinic — Health Library. View source
“The weight you gain before your period is fat.”
In the second half of the cycle the body holds on to more water. Gaining body fat within a few days would take a large energy surplus. How much water you retain varies a lot from woman to woman.
More on this: Gained weight before your period? It's usually water
Sources (2)
- Cleveland Clinic: Luteal Phase of the Menstrual Cycle: Symptoms & Length. Cleveland Clinic — Health Library. View source
- American College of Obstetricians and Gynecologists: The Menstrual Cycle: Menstruation, Ovulation, and How Pregnancy Occurs. ACOG. View source
“People eat more before their period.”
A meta-analysis of 15 data sets with 330 participants found an average of 168 kcal more per day in the second half of the cycle. So the hunger is real and not a lack of willpower. The number is an average; yours can be quite different.
More on this: Cravings across the cycle: before your period, around ovulation, during
Sources (1)
- Tucker, J. A. L., McCarthy, S. F., Bornath, D. P. D. et al. (2025): The Effect of the Menstrual Cycle on Energy Intake: A Systematic Review and Meta-analysis. Nutrition Reviews 83(3), e866–e876. View source
“If your period stops while training, you're in great shape.”
Often it means there hasn't been enough energy for training and basic needs over a longer period, known in sport as RED-S. It's a warning sign, not proof of fitness. If your period has been gone for three months or longer, see a gynaecologist, even if you feel fine.
More on this: When your period stops, it's not a success
Sources (2)
- 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
- NHS (revised 2026): Missed or late periods. NHS, 12 June 2026. View source
“Your period stops because you're low on iron.”
It's usually the other way round: heavy bleeding costs iron, but iron deficiency doesn't make bleeding stop. When a period goes missing, too little available energy is a far more common cause. Reaching for iron tablets then usually treats the wrong thing.
More on this: Iron, periods and exercise: test first, then supplement
Sources (2)
- 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
- National Institutes of Health, Office of Dietary Supplements: Iron — Fact Sheet for Health Professionals. NIH ODS. View source
“If you're tired, taking iron can't hurt.”
Tiredness has many possible causes, and too much iron isn't harmless. Stomach and gut complaints are common, and the body has no effective way to get rid of an excess. Get tested first and let your doctor set the dose.
More on this: Iron, periods and exercise: test first, then supplement
Sources (2)
- National Institutes of Health, Office of Dietary Supplements: Iron — Fact Sheet for Health Professionals. NIH ODS. View source
- Pasricha, S.-R., Tye-Din, J., Muckenthaler, M. U. & Swinkels, D. W. (2021): Iron deficiency. The Lancet 397(10270), 233–248. View source
“A normal blood count rules out iron deficiency.”
Haemoglobin only drops once the stores are already empty. Ferritin shows how full they are. In a study of more than 1,000 young women, the body started absorbing more iron once ferritin fell below about 50 µg/l. Exactly where the cut-off lies is disputed.
More on this: Iron deficiency without anaemia: when the blood count is normal
Sources (2)
- Pasricha, S.-R., Tye-Din, J., Muckenthaler, M. U. & Swinkels, D. W. (2021): Iron deficiency. The Lancet 397(10270), 233–248. View source
- Galetti, V., Stoffel, N. U., Sieber, C. et al. (2021): Threshold ferritin and hepcidin concentrations indicating early iron deficiency in young women based on upregulation of iron absorption. EClinicalMedicine 39, 101052. View source
“Heavy periods can lead to iron deficiency.”
They're one of the main causes of iron deficiency in women, with or without anaemia. A 2023 review describes how both are often brushed off as normal, by women themselves and in doctors' surgeries alike.
More on this: Heavy periods: how much is too much?
Sources (2)
- Munro, M. G., Mast, A. E., Powers, J. M. et al. (2023): The relationship between heavy menstrual bleeding, iron deficiency, and iron deficiency anemia. American Journal of Obstetrics & Gynecology 229(1), 1–9. View source
- NHS (revised 2024): Heavy periods. NHS, 19 September 2024. View source
“There's almost never anything behind heavy bleeding.”
A 2025 meta-analysis of more than 41,000 patients found a bleeding disorder in 30 %, and in 39 % of adolescents. Heavy bleeding that disrupts your life or has gone on for a while should be checked by a doctor.
More on this: Heavy periods: how much is too much?
Sources (1)
- Comishen, K. J., Bhatt, M., Yeung, K. et al. (2025): Etiology and diagnosis of heavy menstrual bleeding among adolescent and adult patients: a systematic review and meta-analysis of the literature. Journal of Thrombosis and Haemostasis 23(3), 863–876. View source
“Severe period pain is normal.”
Pain that regularly keeps you from school, work or training, or that painkillers don't touch, is not a normal amount. Endometriosis can be behind it. According to the WHO, diagnosis takes 4 to 12 years on average.
More on this: Endometriosis: why diagnosis takes so long
Sources (2)
- World Health Organization (2025): Endometriosis – Fact sheet. WHO, 15 October 2025. View source
- De Corte, P., Klinghardt, M., von Stockum, S. et al. (2025): Time to Diagnose Endometriosis: Current Status, Challenges and Regional Characteristics – A Systematic Literature Review. BJOG 132(2), 118–130. View source
“Endometriosis can only be diagnosed with surgery.”
According to the WHO it can also be identified from symptoms and imaging such as ultrasound or MRI, and treatment can start without surgery first. The 2025 German-language guideline puts transvaginal ultrasound at the centre of the examination.
More on this: Endometriosis: why diagnosis takes so long
Sources (2)
- World Health Organization (2025): Endometriosis – Fact sheet. WHO, 15 October 2025. View source
- Burghaus, S., Schäfer, S. D., Bär, K. J. et al. (2026): Diagnosis and Therapy of Endometriosis. Guideline of the DGGG, OEGGG and SGGG (S2k-Level, AWMF Registry No. 015/045, April 2025). Geburtshilfe und Frauenheilkunde 86(2), 133–188. View source
“PMDD is all in your head.”
PMDD has been recognised as a mental health diagnosis in its own right since 2013. A 2024 meta-analysis of about 50,000 participants puts it at 3.2 % when the diagnosis was confirmed. It counts as confirmed once symptoms have been recorded daily over two cycles.
More on this: PMDD: when it's more than PMS
Sources (1)
- Reilly, T. J., Patel, S., Unachukwu, I. C. et al. (2024): The prevalence of premenstrual dysphoric disorder: Systematic review and meta-analysis. Journal of Affective Disorders 349, 534–540. View source
“If your mood crashes before your period, it's always PMDD.”
For some people, symptoms of an existing condition such as depression, panic disorder or an eating disorder get worse before the period but don't go away afterwards. A 2022 review found clear signs of this across several mental health conditions. That isn't PMDD, and it's treated differently.
More on this: PMDD: when it's more than PMS
Sources (1)
- Nolan, L. N. & Hughes, L. (2022): Premenstrual exacerbation of mental health disorders: a systematic review of prospective studies. Archives of Women’s Mental Health 25(5), 831–852. View source
“Menopause starts at 50 and is over in a year or two.”
It usually affects women between 45 and 55, but can come earlier. Symptoms typically last seven to nine years, sometimes longer, and change along the way.
More on this: Perimenopause: the years hardly anyone talks about
Sources (1)
- NHS: Menopause. NHS. View source
“You can't get pregnant during perimenopause.”
Pregnancy is still possible. The NHS advises continuing contraception: from 50, until one year after your last period; between 40 and 49, until two years after it.
More on this: Perimenopause: the years hardly anyone talks about
Sources (1)
- NHS: Menopause. NHS. View source
“Leaking urine during sport only happens in jumping sports.”
A 2026 analysis of 32 studies with more than 4,600 female athletes aged 18 to 45 found no clear difference between sports, including between those with and without jumping. Frequency was most clearly linked to training volume.
More on this: Pelvic floor: incontinence is common – and very treatable
Sources (1)
- Domínguez-Pérez, N., Sevilla-Arrabal, I., Navarro-Brazález, B. et al. (2026): Urinary Incontinence in Women Athletes: Umbrella Review and Meta-analysis of Sport-Related Factors. Sports Medicine 56(9), 2185–2208. View source
“Pelvic floor training helps with bladder leakage.”
According to a 2018 Cochrane review, targeted pelvic floor training can cure or improve urinary incontinence. Another Cochrane review from 2024 notes that the international consultation recommends it as first-line treatment.
More on this: Pelvic floor: incontinence is common – and very treatable
Sources (2)
- Dumoulin, C., Cacciari, L. P. & Hay-Smith, E. J. C. (2018): Pelvic floor muscle training versus no treatment, or inactive control treatments, for urinary incontinence in women. Cochrane Database of Systematic Reviews 10, CD005654. View source
- Hay-Smith, E. J. C., Starzec-Proserpio, M., Moller, B. et al. (2024): Comparisons of approaches to pelvic floor muscle training for urinary incontinence in women. Cochrane Database of Systematic Reviews 12, CD009508. View source
“A pelvic floor programme after birth prevents leakage for everyone.”
As a general programme for everyone after birth, it makes little difference according to Cochrane. Started early in pregnancy, it probably lowers the risk of leakage late in pregnancy and afterwards for women without symptoms.
More on this: Pelvic floor: incontinence is common – and very treatable
Sources (1)
- Woodley, S. J., Lawrenson, P., Boyle, R. et al. (2020): Pelvic floor muscle training for preventing and treating urinary and faecal incontinence in antenatal and postnatal women. Cochrane Database of Systematic Reviews 5, CD007471. View source
“Pain during sex is something you just have to put up with.”
It has causes that can be treated. In a randomised trial of 212 women with provoked vestibulodynia, physiotherapy reduced pain during sex more than a numbing cream. If sex keeps hurting, that's reason enough to make an appointment.
More on this: Pain during sex: common, but not normal
Sources (1)
- Morin, M., Dumoulin, C., Bergeron, S. et al. (2021): Multimodal physical therapy versus topical lidocaine for provoked vestibulodynia: a multicenter, randomized trial. American Journal of Obstetrics & Gynecology 224(2), 189.e1–189.e12. View source
“After giving birth, pain during sex goes away within a few weeks.”
A meta-analysis of more than 11,000 women found it in 42 % two months after birth and still in 22 % between six and twelve months. It usually improves over time, but not for everyone.
More on this: Pain during sex: common, but not normal
Sources (1)
- Banaei, M., Kariman, N., Ozgoli, G. et al. (2021): Prevalence of postpartum dyspareunia: A systematic review and meta-analysis. International Journal of Gynecology & Obstetrics 153(1), 14–24. View source
“Women have completely different heart attack signs from men.”
Chest pain is the most common sign in women too: 74 % had it, compared with 79 % of men. But women more often have pain between the shoulder blades, nausea or breathlessness. If chest pain lasts longer than five minutes, call emergency services straight away (112 in Europe).
More on this: Heart attacks in women: the signs are not “atypical”
Sources (2)
- van Oosterhout, R. E. M., de Boer, A. R., Maas, A. H. E. M. et al. (2020): Sex Differences in Symptom Presentation in Acute Coronary Syndromes: A Systematic Review and Meta-analysis. Journal of the American Heart Association 9(9), e014733. View source
- German Heart Foundation (Deutsche Herzstiftung): Herzinfarkt: Anzeichen erkennen und richtig handeln. herzstiftung.de. View source
“With unclear heart symptoms, it's better to wait and see.”
On average women reach hospital later than men, mainly because they wait longer before getting help. The German Heart Foundation advises calling an ambulance for nausea, breathlessness or upper abdominal pain too, if they're stronger than ever before.
More on this: Heart attacks in women: the signs are not “atypical”
Sources (2)
- Hu, D., Duan, Y., Song, J. et al. (2026): Sex disparities in pre-hospital delay in patients with acute myocardial infarction: a systematic review and meta-analysis. BMC Cardiovascular Disorders 26. View source
- German Heart Foundation (Deutsche Herzstiftung): Herzinfarkt: Anzeichen erkennen und richtig handeln. herzstiftung.de. View source
“Pre-eclampsia is over once the baby is born.”
According to a 2024 meta-analysis of 22 studies, affected women later have about twice the risk of cardiovascular disease. It shows up in the first years afterwards and is still visible decades later.
More on this: Heart attacks in women: the signs are not “atypical”
Sources (1)
- Inversetti, A., Pivato, C. A., Cristodoro, M. et al. (2024): Update on long-term cardiovascular risk after pre-eclampsia: a systematic review and meta-analysis. European Heart Journal – Quality of Care and Clinical Outcomes 10(1), 4–13. View source
“The more protein, the more muscle.”
The ISSN gives 1.4 to 2.0 g per kilogram of body weight per day as enough for most people who train. Above that range, no extra benefit for building muscle has been shown.
More on this: How much protein do you need if you train?
Sources (1)
- 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
“Sports nutrition advice has been well studied in women.”
Most of the studies were done with men and the results were then carried over. The ISSN points this out itself in its position stand on female athletes. The recommendations are a guide, not a law of nature.
More on this: How much protein do you need if you train?
Sources (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
“A calorie calculator tells you exactly how much you need.”
An equation with four inputs can't capture what differs between two people, such as muscle mass or how much you move without noticing. Two women entering the same details can differ by several hundred kilocalories in what they actually burn. The number is a starting point; what you observe beats the formula.
More on this: Calculating calorie needs: what the number can and can't do
Sources (1)
- Mifflin, M. D., St Jeor, S. T. et al. (1990): A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition 51(2), 241–247. View source
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