The Four-Week Cycle and Sport

Hormone cycles are contributing to a higher rate of ACL injuries in women’s sport

It is no secret to over half of the population that there are ebbs and flows within each monthly cycle. This is a broad statement and does not account for women who do not menstruate for many reasons, including amenorrhea, PCOS, hormonal conditions, or other gender-specific factors. 

In sport, however, the calendar rarely accommodates biology. Match day does not care which phase of the cycle you are in. You are expected to show up and perform, whether you are in a high-energy phase or on day one of menstruation. 

As women’s sport enters a new era of increased sponsorship, greater visibility, and commercial growth, however, questions are being raised about whether the gender research gap is limiting the athletes’ performance and contributing to injury patterns.  

For years, training programmes have largely been designed around male physiology. As investment grows, the question arises: Are female athletes still forced to operate within systems not built for their bodies? 

One area where this conversation becomes urgent is the rise in ACL injuries in women’s sport. Professor Kirsty Elliott-Sale, Head of the Centre of Excellence for Women in Sport at Manchester Metropolitan University, has dedicated much of her research to the effects of female reproductive hormones on athletic performance. 

Speaking on The Game Changers podcast, Elliott-Sale discussed controlled studies suggesting that increased levels of oestrogen, typically around day twelve of the menstrual cycle, may be associated with a greater risk of non-contact ACL injury. The theory centres on hormonal influence on ligament laxity and neuromuscular control — yet there is something of a dichotomy. 

Anecdotally, many female athletes report sustaining ACL injuries during menstruation, around days one to four of the cycle, when oestrogen levels are comparatively low.  

This was the case for Olivia Boscaccy, one of St Andrews’ most accomplished footballers. She tore her ACL in July 2019 during pre-season conditioning, taking a step to turn onto her left foot. She recalls being on her period at the time. 

Her injury was diagnosed quickly in the US, with an MRI confirming damage to her ACL, MCL, and meniscus within 24 hours. Boscaccy’s injury occurred before this research became more widely discussed, and she said that menstrual health was never raised as a possible contributing factor.  

She was also unaware at the time that female athletes are statistically more prone to ACL injuries, and noted that structured prevention work was not part of her team's training programme until after multiple injuries began occurring within her cohort.  

The science, Elliott-Sale emphasises, is not settled; the body of high-quality research remains limited, and hormones may represent only one variable among many. Training load, recovery structures, biomechanics, and inherently male-centred programme design may also contribute. 

Hormones may influence risk, but they do not operate in isolation. For athletes, the injury is rarely theoretical. 

Fourth year Anja Colombi tore her ACL in October 2024 while playing away in a netball match in Edinburgh. Her diagnosis was not immediate; after visiting A&E, she was discharged with a splint and crutches, but no MRI. Weeks later, a consultant confirmed a full ACL rupture and partial meniscus tear. 

Colombi reflected, “I saw his face change when he did the tests. He said he was almost certain it was my ACL. I just burst into tears.” 

Colombi said that no one discussed menstrual cycle timing at any stage of her diagnosis or rehabilitation. She added that much of the information she received about her injury and recovery came from her own research rather than from her medical team. 

Now further into recovery, she believes that rehabilitation programmes should better reflect the realities of female physiology: “Rehab plans are set, and you just follow them. I think there should be more flexibility and more structure around the cycle.”  

She also thinks that injury prevention education needs greater emphasis and that the coach holds the responsibility for educating themselves and their team.  

Boscaccy also reflected on how little her rehabilitation programme accounted for hormonal variation. “It was very by-the-book,” she explained, “with no variation or cycle syncing.” 

Six years on from surgery, she has recently torn her meniscus again.  

Boscaccy feels that the long-term toll and the lack of emphasis on prevention from the outset are missing from the conversation: “You think surgery fixes it, but every time it hurts, there’s that fear of tearing it again.”  

If hormones may influence performance or injury risk, cycle-specific training appears logical in theory. Team sport complicates that logic. Can a squad realistically individualise training around twenty different hormonal profiles, or does the nature of competition require uniform preparation regardless of physiology?

Education for coaches appears to be increasing, particularly at elite levels. Research and investment at clubs such as Arsenal Women indicate a growing recognition of menstrual health within professional sport. In addition, UEFA-linked research panels are examining the impact of menstrual cycles on performance.  

Investment in women’s sport is no longer marginal, yet there is a question as to whether this education empowers athletes or risks over-medicalising their bodies. As women’s sport becomes more commercially valuable, pressure to optimise performance increases. 

A source in the US told The Saint that there was an incident in which a collegiate lacrosse coach allegedly placed an entire team on hormonal contraception, though this claim could not be independently verified. It does, however, raise broader ethical questions. 

Hormonal contraception can regulate menstrual cycles; in theory, synchronising cycles could simplify training periodisation. Hormonal contraception, however, is a medical decision with implications beyond sport, having potential impacts on fertility, mental health, and long-term well-being. 

The issue is not whether hormonal contraception is valid — for many women, it is a positive and personal healthcare choice. The question is who makes that decision and under what influence. 

If hormonal regulation were ever normalised as a performance strategy, where would that leave athletes for whom hormonal contraception is unsuitable, whether for medical, ethical, or religious reasons? Could this unintentionally exclude some women from participation? 

As research into hormone patterns in sport expands, the landscape may shift. Whether that shift will lead to better support or increased control remains uncertain. 

The four-week cycle is not a weakness; it is a biological reality. As women’s sport grows in audience, sponsorship, and prestige, so too does the value placed on marginal gains. The question facing the industry is not simply whether hormones influence injury or performance, but how that knowledge will be used. 

Will it lead to better education and athlete-centred support? Or, as the price of success rises, will physiology become something to manage? For now, the scientific research persists, the questions remain open, and the four-week cycle continues to confuse.  

Image by Elodie Cowan