In a previous blog we explored how underrepresented women are in scientific research and we recommended that we need more studies in female athletes. However, research is slow, and takes time. Nevertheless, we see plenty of sex-specific recommendations for female athletes. These recommendations are not always supported by evidence because research is still lagging behind. One of the areas that has seen a lot of attention, and where lots of very specific guidelines are being developed, is training based on menstrual cycle phase. A recent review (1) addressed the question: do we have enough evidence to make meaningful recommendations for training based on phases of the menstrual cycle?
The authors included Lauren Colenso-Semple and Stuart Phillips from McMaster University in Canada. They joined forces with Kirsty Elliott-Sale at Manchester metropolitan University in the UK. The lab of Dr Phillips has been a long-time leader in the research into protein metabolism in men and women and Kirsty Elliot-Sale, who also wrote our previous blog is an expert in menstrual cycle phase in athletes.
With a surging growth in menstrual cycle tracking tools there has been an assumption that this will inform better training. And although the idea is attractive, there are a couple of really important questions:
Is there evidence to support menstrual cycle-based training? And
If there is evidence, how should training differ in different phases of the menstrual cycle?
But there are other important questions as well, such as:
Are these recommendations different for women who use oral contraceptives? (Hint: it is likely that it will, given that oral contraceptive users have different hormonal profiles to women with menstrual cycles, as we discussed in a previous blog) And
Are the tracking devices accurate enough in the first place? (Hint: it is likely that most of them are not)
The recently published review (1) aimed to fill some knowledge gaps related to how menstrual cycle phases might affect gains in muscle size and strength as well as exercise performance. The authors conducted an umbrella review of meta-analyses and systematic reviews to critically evaluate and summarise the current state of knowledge on the impact of menstrual cycle phase on resistance exercise performance and training adaptations. The authors carefully assessed often cited papers supporting the concept that menstrual cycle phase-based training is an effective practice.
The authors assessed studies that investigated differences between menstrual cycle phases in strength, exercise performance, and hypertrophy. The main conclusion from the authors was that there was very little evidence, and in most cases very low level evidence, with a lot of inconsistent findings. The only area where trivial-to-small effects of menstrual cycle phase were found was on indirect markers of delayed onset of muscle soreness, but the authors also concluded that the validity of such markers is questionable.
Should we have different recommendations in different phases of the menstrual cycle?
There is no doubt that there are profound differences in the in the magnitude of hypertrophic response to strength training between individuals. This can be observed in women but also in men.
Studies that compared the hypertrophic response to resistance exercise training between men and women indicate equivalent relative gains in muscle size and, for the most part, strength (2). These observations make it less likely that there are differences in the effects of resistance exercise training within a person, even though ovarian hormones levels may vary during the menstrual cycle. In the absence of high-quality evidence to indicate that fluctuations in ovarian hormones during a menstrual cycle substantially influence acute strength performance or muscular adaptations, it is premature to assume that it is essential to adapt training to the phase of the menstrual cycle.
It is premature to assume that it is essential to adapt training to the phase of the menstrual cycle.
Practical recommendations
In the absence of evidence to support designing resistance training programs based on menstrual cycle phase, coaches and athletes should tailor an exercise plan to the individual. The influence of the menstrual cycle could be a factor to consider in program design, but it is only one thing in a longer list of other factors like short term and long term goals, fatigue, sleep quality, stress, injury, motivation, program enjoyment and logistics.
It is clear that menstrual symptoms can influence exercise performance in some women and thus it may be helpful for those women to document their symptoms for reviewing long-term progress and adjusting a program.
Or in the authors words: When reviewing the evidence as a whole—and the methodological shortcomings therein—we propose it is highly premature to conclude that short-term fluctuations in ovarian hormones appreciably influence acute exercise performance or longer-term adaptations to resistance training. Thus, the development of resistance exercise training prescriptions based on cyclical hormonal changes is not an evidence-based approach.
References
L.M. Colenso-Semple, A.C. D'Souza, K.J. Elliott-Sale and S.M. Phillips. 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. Volume 5 – 2023
Roberts BM, Nuckols G, Krieger JW. Sex differences in resistance training: a systematic review and meta-analysis. J Strength Cond Res. (2020) 34(5):1448–60
