Cycle and Training: Should You Train According to Your Cycle? What the Research Actually Shows

Cycle-based training sounds logical: go all out in the first half, ease off in the second. But the major review studies find only tiny differences between phases. What really matters are your symptoms, your iron levels, your sleep, and a cycle that doesn't disappear.

Tuesday evening, day two of your period. Your training plan says heavy squats, five sets. Over the weekend you watched a video on your phone: in the second half of the cycle you should take it easy, chase personal bests in the first half, and stick to yoga during your period. You do the quick mental maths, aren't quite sure which phase you're in, and wonder whether you're getting it wrong no matter what you choose.

Or maybe the opposite is true for you: you feel strong on exactly that day, and yet an app tells you you're in your weak phase.

We looked at what major review studies show about cycle and performance, strength training, and the pill — and what is known about period pain, iron, and sleep — as well as what the Swiss Federal Office of Sport recommends to coaches. The short answer upfront: a fixed phase-based plan cannot be derived from the research. Your own wellbeing, carefully tracked, is the better compass.

Should you train according to your cycle?

A fixed training plan based on cycle phases cannot be derived from the research. A 2020 meta-analysis of 78 studies found only trivial performance differences between phases and explicitly recommended a personal approach rather than general rules. It makes sense to pay attention to how you feel and to track it.

Cycle-based training, often called "cycle syncing", promises a lot: more strength, faster progress, fewer injuries when you align your sessions with your hormones. The idea behind it: the sex hormones oestrogen and progesterone fluctuate considerably throughout the cycle.

Whether this translates into a measurable difference in sport, however, is another question. The largest analysis to date — the meta-analysis by McNulty et al. from 2020 — found barely any. A meta-analysis is a study that pools the results of many individual studies so that chance findings carry less weight.

The authors themselves write that no general recommendations can be drawn from their data. Instead, they recommend paying attention to each individual woman's response to her cycle. That is exactly what this article is about: not a plan for everyone, but finding out what happens in your case.

This does not mean your cycle is irrelevant. Period pain, fatigue, heavy bleeding, low iron levels, or a missing period can all affect your training. These points are well supported by evidence and matter more than whether today is day 9 or day 19.

What happens during the cycle, and why is the phase so hard to pin down?

A cycle begins on the first day of the period and divides roughly into the time before ovulation and the time after it. In an analysis of 612,613 cycles, the first half lasted an average of 16.9 days, but typically varied between 10 and 30 days. Your phase can therefore only be estimated from the calendar alone.

In the first half of the cycle, the follicular phase, an egg matures in one of the ovaries and oestrogen levels rise. After ovulation comes the luteal phase, during which a lot of progesterone is also produced. If no pregnancy occurs, both hormones drop and the next period begins.

Many training plans assume a 28-day cycle with ovulation on day 14. Reality is messier. Bull et al. analysed 612,613 cycles from 124,648 users of a cycle app in 2019, published in npj Digital Medicine. The mean cycle length was 29.3 days, the follicular phase 16.9 days, and the luteal phase 12.4 days. In most cycles, the follicular phase fell somewhere between 10 and 30 days, and the luteal phase between 7 and 17 days.

The Canadian-British research group around Colenso-Semple emphasised the same point in 2023 from a sports science perspective: counting calendar days and your own cycle history shows whether a cycle is regular, but not when ovulation occurred. For that, a urine or blood test is needed. Many studies that phase-based plans rely on did not verify this.

For you, this means: when an app tells you you're in the luteal phase today, that is an estimate — and a shaky foundation for a plan that adjusts day by day based on phase.

Are you less able to perform in certain cycle phases?

If at all, only very slightly. The meta-analysis by McNulty et al. (Sports Medicine 2020) with 78 studies found performance in the early follicular phase — around the period — to be on average trivially lower than in other phases. The authors rated the quality of the studies as low, and the variation between studies was large.

Kelly McNulty's team at Northumbria University in the UK analysed 78 studies of women with a natural, regular cycle who were not using hormonal contraception.

Comparing the early follicular phase with all other phases, the pooled effect size was minus 0.06. This is a measure of the size of a difference, where even 0.2 is considered small. The largest individual difference was between the early and late follicular phase, at minus 0.14 — also small.

The authors themselves are cautious in their interpretation: because the effect is trivial, the studies vary widely, and many were methodologically weak, no general guidelines can be derived. Instead, they recommend paying attention to each individual woman's response.

For your daily life, this means: if you feel weaker in the first days of your period, you are not imagining it — that is exactly where the small difference was found. If you feel strong during that time, that is equally normal. Skipping a session simply because the calendar shows a particular phase cannot be justified by this data.

Does strength training in the first half of the cycle build more muscle?

This is not supported by evidence. A 2023 overview of five systematic reviews concluded that it is premature to link strength performance or muscle gain to short-term hormonal fluctuations. The widely cited studies on training in the follicular phase had, in the authors' view, significant methodological weaknesses.

Lauren Colenso-Semple and Stuart Phillips of McMaster University in Canada, together with Kirsty Elliott-Sale from the UK, summarised five meta-analyses and systematic reviews in 2023 in the journal Frontiers in Sports and Active Living. This is an overview of overviews.

Their finding is stated in the title: the current body of evidence shows no effect of cycle phase on short-term strength performance or on adaptation to strength training. The results of the individual reviews diverged widely, and they found little high-quality evidence for meaningful differences.

They looked particularly closely at two studies that recommendations for follicular-phase strength training often rely on. For one, they doubt whether the phases were correctly identified at all; the other they consider an invalid comparison, partly because a 28-day cycle was assumed rather than verified, and because women on the pill also took part.

Their practical advice is straightforward: adapt training plans to the individual and track cycle symptoms, as these can affect performance in some women. For muscle building, what matters is what applies to everyone: train regularly, increase the load gradually, and recover adequately. You can read more in the article on strength training after 40.

Strength training after 40

Can you exercise during your period, and does movement help with period pain?

Yes, exercising during your period is fine and can even help. A 2019 Cochrane review of 12 studies with 854 women found that exercise can significantly reduce period pain — by around 25 millimetres on a 100-millimetre pain scale. However, the certainty of the evidence is low.

Cochrane is an international network that summarises studies according to fixed rules and evaluates their quality. Armour et al. reviewed in 2019 whether exercise helps with primary dysmenorrhoea — period pain without an underlying condition. Gentler forms such as stretching, core training, and yoga were studied alongside more intense forms such as aerobics.

Compared with no treatment, pain was significantly lower with exercise, regardless of how intensely participants trained. In most studies, women exercised at least three times per week for around 45 to 60 minutes; whether shorter or less frequent sessions work equally well remains open. The studies were small and not blinded, so Cochrane rates the certainty of the evidence as low to very low.

That symptoms play a real role in sport is shown by a large survey: Bruinvels et al. surveyed 6,812 physically active women not using combined hormonal contraception via a sports app (British Journal of Sports Medicine 2021). The most commonly reported symptoms were mood changes or anxiety (90.6 percent), fatigue (86.2 percent), abdominal cramps (84.2 percent), and breast pain (83.1 percent). The more symptoms a woman experienced, the more likely she was to miss training sessions or competitions. Several authors work for a company with its own cycle app — this is worth noting for context.

The independent German health portal gesundheitsinformation.de of IQWiG lists heat and pain relievers such as ibuprofen or naproxen alongside exercise as options. About one in ten women has period pain severe enough to prevent her from managing daily life as usual for one to three days per month. If the pain is very severe or worsening, the portal recommends gynaecological assessment, as conditions such as endometriosis or fibroids may be involved.

In practice: if you feel fit on a period day, train as planned. If you have cramps, a lighter session or a walk may do more good than nothing at all. Talk to your doctor or pharmacist about which pain relievers suit you.

Does the pill change your performance in sport?

Barely, on average. A meta-analysis of 42 studies with 590 participants (Elliott-Sale et al., Sports Medicine 2020) found performance in women on the pill to be at most trivially lower than in women with a natural cycle. Performance remained consistent across the pill cycle.

The pill suppresses ovulation and replaces natural hormonal fluctuations with steady synthetic hormones, usually with a break of a few days. Whether this changes sport performance was investigated by Kirsty Elliott-Sale et al. in the same issue of Sports Medicine in which the cycle meta-analysis appeared.

Their finding: women on the pill may on average perform slightly worse than women with a natural cycle, but the difference is most likely trivial. Between pill-taking days and the pill-free interval, the team found virtually no difference. 83 percent of the studies were rated by the authors as having moderate, low, or very low quality.

Here too, the conclusion is the same: no general rules, but a personal approach if performance matters to you. The decision for or against a method of contraception involves far more than sport. If you want to change your contraception, discuss it with your gynaecologist and do not stop a preparation on your own.

Why is iron so important for women who exercise and have periods?

With every period you lose blood and therefore iron. The DGE and ÖGE therefore recommend 16 milligrams of iron per day for women with periods, and 11 for men. According to a 2019 review, approximately 15 to 35 percent of studied groups of female athletes had iron deficiency, compared with 5 to 11 percent of male athletes.

Iron is found in the red blood pigment that carries oxygen to the muscles. When iron is low, you tire more quickly and feel run down; the Austrian health portal gesundheit.gv.at lists fatigue, tiredness, and feeling cold as typical signs, and heavy menstrual bleeding as a common cause of iron deficiency.

The reference values of the German Nutrition Society (DGE), which apply jointly with the Austrian Nutrition Society (ÖGE), therefore distinguish: 16 milligrams per day for women with periods, 11 milligrams for women without periods and for men, 14 milligrams after menopause. The values were last derived in 2023.

Sim et al. compiled in 2019 in the European Journal of Applied Physiology what is known about iron in sport. Iron deficiency mainly affects women and endurance athletes. One contributing factor is the hormone hepcidin, which regulates iron metabolism and rises with exercise. What blood thresholds should apply for female athletes remains disputed among experts.

If you feel persistently tired despite good recovery, a blood test is worthwhile. The most important value is ferritin, stored iron. What it means and what thresholds exist, you can read in the article on ferritin and iron status. Do not take iron supplements on a hunch; whether and how much you need is a matter for your doctor.

Through your diet you can do a lot yourself: iron-rich foods such as meat and fish, or plant-based options like legumes and wholegrains, combined with vitamin C — for example from peppers, broccoli, or a glass of orange juice. Vitamin C can promote iron absorption, writes gesundheit.gv.at; iron from plants is less well absorbed by the body than iron from meat and fish.

Ferritin and iron status

Do you sleep worse around your period?

Many women experience this, and studies confirm the feeling. According to a review by Baker and Driver (Sleep Medicine 2007), subjective sleep quality is rated worst around the time of the period. However, sleep duration and architecture remain largely unchanged in healthy women.

Fiona Baker and Helen Driver summarised in 2007 what is known about sleep, the internal clock, and the menstrual cycle. In healthy women, the timing and composition of sleep remain quite stable across the cycle. In the luteal phase, sleep lab measurements show only small changes, such as slightly less REM sleep — the dream sleep phase.

The subjective experience is different: around the time of the period, women rate their sleep as worst.

This still matters for your training, because how recovered you feel affects how hard a session feels. If you feel tired after several poor nights, choosing a lighter session is a sensible decision — because of the sleep, not the phase. You can read about how exercise and sleep are connected in the article on exercise and sleep.

Around menopause, sleep changes more noticeably — for example through night sweats. There is a separate article on menopause and sleep.

Exercise and sleep · Menopause and sleep

When should your cycle raise a red flag during sport?

If your period has been absent for three months or more and you are not pregnant, breastfeeding, or going through menopause. The Austrian health portal lists excessive exercise, underweight, and eating disorders as possible causes and advises seeing a gynaecologist early. This is not a sign of training hard enough.

Specialists refer to secondary amenorrhoea when a woman who has previously had her period goes three months or more without bleeding. This is the definition given on gesundheit.gv.at, the public health portal of Austria. Alongside pregnancy, breastfeeding, and menopause, the portal lists competitive sport, excessive exercise, eating disorders, and underweight as causes.

In sport, the International Olympic Committee (IOC) published a consensus statement in 2023 on Relative Energy Deficiency in Sport, abbreviated as REDs. This refers to a state in which you are taking in too little energy from food relative to what you expend in training. According to the statement, it affects both female and male athletes and can impair both health and performance.

A missing period is therefore not proof that you are training hard enough — it is a signal that your body needs something different. Very irregular cycles or new, severe symptoms also belong in a gynaecological practice.

Exception: hormonal contraceptives such as the pill or a hormonal IUD can reduce or shorten bleeding, as noted on gesundheitsinformation.de. This is then a known effect of the preparation. If you are unsure whether that is the reason in your case, ask at your gynaecological practice.

How do you talk to your coach about your cycle?

As naturally as you would talk about nutrition or recovery — but only if you want to. The Swiss Federal Office of Sport (BASPO) advises coaches on its mobilesport.ch platform to bring up the topic openly, never to pressure anyone, and to adjust training intensity, duration, or type as needed.

A dossier on the female cycle in sport was published on mobilesport.ch, the BASPO practice platform, in January 2026, developed with Jugend+Sport and Swiss Olympic. It recommends addressing the cycle as a normal topic, similar to nutrition or recovery. At the same time, it notes that not all athletes want to talk about it and that coaches should never pressure anyone to share personal topics.

As a tool, the dossier suggests a cycle diary: over two cycles, you note energy, mood, sleep, and symptoms daily on a scale of 1 to 5, with particular attention to the days before and during your period. The aim is explicitly not to judge whether a session was "good" or "bad", but to identify your own pattern. The diary belongs to you and is confidential.

How varied individual experience is was shown by a small interview study with 15 national-level rugby players (Findlay et al., British Journal of Sports Medicine 2020). 93 percent reported cycle symptoms, 67 percent felt these affected their performance, and about two thirds self-medicated. The authors call for coaches and support staff to know more about the cycle and to discuss it more openly.

For coaches — and also for training partners — this means above all: listen rather than impose rules. A sentence like "I have bad cramps today, let's reschedule the interval session" is information about your day, not an excuse.

How the YUTHI app helps you

In the Cycle section of the YUTHI app, you tap when your period starts and ends and how heavy the bleeding is. Under "Body" you log cramps, headaches, back pain, breast tenderness, cravings, and nausea; under "Wellbeing" you record high or low energy, good or low mood, and poor nights' sleep. This is your cycle diary — no notebook required. Because cycle data are specially protected health data, the section only saves anything once you have given your explicit consent.

The app shows you your cycle day and, from two recorded cycles onward, a prediction for your next period, the average length of your cycles, and how much they vary. The "Body & Wellbeing" tile shows what you have entered most often in the last 28 days. This lets you recognise your own pattern rather than measuring yourself against an average. YUTHI is not a contraceptive and does not predict fertile days.

Your Coach knows the research from this article: it knows that performance differs only trivially across the cycle according to McNulty 2020, and therefore does not suggest changing your plan based on phase alone. It knows the 16 milligrams of iron recommended by DGE for women with periods, and when ferritin is low it suggests iron-rich foods and vitamin C first, supplements last. You can enter your ferritin value under Blood values. In the Sleep section, a note during your period reminds you that sleep often feels worse during those days, even though sleep duration and architecture remain the same.

For conversations at your gynaecological practice, the report for your doctor summarises your logged period start dates and cycle lengths. And how is it for you: do you actually feel weaker during training on period days, or has the calendar just been telling you that you should?

YUTHI app

Frequently asked questions

Is cycle-based training scientifically supported?

No, not as a fixed phase-based plan. The meta-analysis by McNulty et al. (2020) found only trivial performance differences, and a 2023 overview considered it premature to align strength training with cycle phase. Both recommend a personal approach.

Should I avoid strength training during my period?

Not if you feel well. No general reason to avoid strength training during your period can be derived from the review studies. If you have severe cramps or feel very tired, a lighter session is a good choice.

Is the injury risk higher in certain cycle phases?

The BASPO dossier on mobilesport.ch notes that hormonal changes around ovulation can slightly increase injury risk, but not systematically. As prevention, it recommends targeted strength and coordination training, which is beneficial regardless.

Does exercise help with period pain?

A 2019 Cochrane review of 854 women found that regular exercise can significantly reduce period pain, regardless of intensity. However, the data are of low quality. If your pain is very severe or worsening, get a gynaecological assessment.

How much iron do I need as a female athlete?

DGE and ÖGE recommend 16 milligrams of iron per day for women with periods. They do not provide a separate figure for female athletes. Whether you are getting too little is shown by a blood test measuring ferritin; take iron supplements only after consulting your doctor.

My period has been missing since I started training more. Is that normal?

No, you should have this checked. If your period has been absent for three months or more, the Austrian health portal advises making an early appointment at a gynaecological practice. Possible causes include high training load and too little energy from food.

Sources

• McNulty KL, Elliott-Sale KJ, Dolan E, et al. The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. Sports Med. 2020;50(10):1813–1827.
• Colenso-Semple LM, D'Souza AC, Elliott-Sale KJ, Phillips SM. Current evidence shows no influence of women's menstrual cycle phase on acute strength performance or adaptations to resistance exercise training. Front Sports Act Living. 2023;5:1054542.
• Elliott-Sale KJ, McNulty KL, Ansdell P, et al. The Effects of Oral Contraceptives on Exercise Performance in Women: A Systematic Review and Meta-analysis. Sports Med. 2020;50(10):1785–1812.
• Bull JR, Rowland SP, Scherwitzl EB, et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ Digit Med. 2019;2:83.
• Armour M, Ee CC, Naidoo D, et al. Exercise for dysmenorrhoea. Cochrane Database Syst Rev. 2019;(9):CD004142.
• Bruinvels G, Goldsmith E, Blagrove R, et al. Prevalence and frequency of menstrual cycle symptoms are associated with availability to train and compete: a study of 6812 exercising women. Br J Sports Med. 2021;55(8):438–443.
• Findlay RJ, Macrae EHR, Whyte IY, et al. How the menstrual cycle and menstruation affect sporting performance: experiences and perceptions of elite female rugby players. Br J Sports Med. 2020;54(18):1108–1113.
• IQWiG. Regelschmerzen. gesundheitsinformation.de, 2023.
• DGE. Referenzwerte für die Nährstoffzufuhr: Eisen. Stand der Ableitung 2023.
• gesundheit.gv.at. Eisen: Bedarf, Quellen und Mangel. 2024.
• Sim M, Garvican-Lewis LA, Cox GR, et al. Iron considerations for the athlete: a narrative review. Eur J Appl Physiol. 2019;119(7):1463–1478.
• Baker FC, Driver HS. Circadian rhythms, sleep, and the menstrual cycle. Sleep Med. 2007;8(6):613–622.
• gesundheit.gv.at. Ausbleiben der Regelblutung (Amenorrhoe) und seltene Regelblutung (Oligomenorrhoe). 2021.
• Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 IOC consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073–1097.
• BASPO, mobilesport.ch. Der weibliche Zyklus im Sport. Dossier 1/26, 2026.