For most of its history, exercise physiology studied men. The reasons given were methodological — hormonal variation was treated as a confound to be avoided rather than a variable to be studied — and the effect was that training and nutrition guidance was derived from male subjects and applied to everyone.
Reviews of the sports science literature have found that female participants have historically made up a minority of subjects, and a smaller minority still in studies of elite performance. The imbalance has narrowed but persists.
The correction under way is welcome. It is also, at this stage, producing more confident claims than the evidence supports, and it is worth separating what is established from what is being marketed.
What is reasonably well established
Symptoms affect training. Surveys of athletes consistently find that a large majority report menstrual symptoms affecting their training or performance at some point. This is self-report, but it is self-report about one's own experience, which is the appropriate method for that question.
Heavy bleeding and iron status matter. Iron deficiency is more common in female athletes, heavy menstrual bleeding is a significant contributor, and iron deficiency has clear effects on endurance performance. This is one of the better-evidenced practical issues and is straightforwardly testable and treatable.
Low energy availability is a serious problem. The syndrome now generally described as relative energy deficiency in sport — insufficient energy intake for training load — has well-documented consequences including menstrual dysfunction, impaired bone health and performance decline. Amenorrhoea in an athlete is a clinical sign, not a convenience.
Bone health consequences are real and can be permanent. Adolescence is a critical window for bone mineral accrual, and disruption during it is not fully recoverable later.
What is less established than the coverage suggests
The idea of training periodisation synchronised to the menstrual cycle — structuring training phases around hormonal phases — has become popular and is being sold commercially.
The evidence base is thinner than the enthusiasm. Systematic reviews examining performance across cycle phases have generally found that effects on performance are small on average and highly variable between individuals, and that study quality in this area is frequently poor.
The most defensible current summary is roughly: group-level effects are small, individual variation is large, and the study designs needed to establish phase-based training benefits mostly have not been done.
This does not mean the approach is wrong. It means that anyone stating confidently which training should happen in which phase is going beyond the evidence.
The individual variation point matters most
Because average effects are small and individual effects are not, the practically useful thing is individual tracking rather than a general protocol.
An athlete who records symptoms, training quality and cycle timing over several months has better information about herself than any published average provides. This is not a sophisticated intervention — it requires a notebook — and it is what most practitioners working in this area actually recommend, as distinct from what is being sold.
The provision problem
Under all of the physiology sits a set of basic logistical issues that receive far less attention and probably affect more athletes.
Kit colour. The decision by a number of prominent teams and tournaments to move away from white shorts followed sustained pressure from athletes and was reported as a significant change. That a change of this magnitude was required to address an obvious problem is itself informative about how these matters have been handled.
Toilet and changing access during training and competition. Frequently inadequate, particularly at community level and in outdoor sports.
Availability of products at venues. Increasingly common at well-resourced facilities and rare elsewhere.
Whether an athlete can tell her coach. Surveys consistently find that a majority of female athletes have never discussed menstruation with a coach, and that the proportion is lower still where the coach is male. The most common reason given is discomfort rather than any belief it is irrelevant.
The coaching conversation
The last of those is the one with the clearest fix.
Coach education programmes that simply include the topic — what to ask, how to ask it, what to do with the answer — have been reported to substantially change whether athletes disclose. The barrier is not usually hostility; it is that neither party has a script.
The practical version is unremarkable: a coach who has said once, at the start of a season, that this is a normal thing to mention and that adjustments are available, gets told about problems. A coach who has never mentioned it does not.
Hormonal contraception
A large proportion of athletes use hormonal contraception, and its effects on performance are frequently asked about.
The evidence is mixed and the effects reported are generally small. Reviews have found no consistent large performance effect in either direction, with considerable variation between preparations and individuals.
The reasons athletes use it vary — cycle control and symptom management are commonly cited alongside contraception — and the decision is properly a clinical one rather than a performance one, given how weak the performance evidence is in either direction.
The summary worth keeping
The research gap was real and is being addressed. The most useful findings so far are about iron, energy availability and bone health, which are clinical and actionable. The phase-based training claims are ahead of their evidence.
And the interventions likely to affect the most athletes are not physiological at all. They are kit, facilities, and whether anyone has said out loud that this is a thing that can be discussed.