Because of the anti-inflammatory effects of oestrogen, the location of oestrogen receptors on skeletal muscle, and the potential for enhancing skeletal muscle sensitivity to anabolic stimuli, it’s feasible to think that whilst oestrogen is dominant in the follicular phase, we may see greater strength or adaptations to resistance training at that time. On the flip side, as we see increases in core temperature, some metabolic changes and weight gain with progesterone dominance during the luteal phase, it’s feasible that during the luteal phase, we experience reductions in strength.

What happens to real life humans?

Popularity for periodising (pun intended) training around the menstrual cycle peaked in the 2010s when a couple of key men in the industry at the time wrote some books and articles and cited a couple of repeatedly referenced pieces of research that highlighted that front-loading training appeared to be beneficial for training performance. Influencers picked up on these few key readings and regurgitated them worldwide (influencers aren’t paid to be scientifically critical, I like to think we all do our best to find the available evidence).

The problem was, all of the data that was available was from really small scale studies. There was one in 7 subjects over just 2 months (literally 7 women being used as justification for how all women should train), that highlighted that training twice a day in the follicular phase and once a day in the luteal phase led to significantly greater changes in maximal strength compared to training regularly throughout the cycle. Another slightly larger study (38 participants) highlighted that front-loading training (5 sessions per week in the follicular phase) led to significant increases in leg lean mass, but training 5 sessions per week in the luteal phase or regularly throughout the cycle did not.

There were a handful of studies like this that were then used as reasoning for all women to structure their training such that most of it was completed early in the cycle, with deloads or generally reduced volume programmed automatically during the week before a bleed.

Ultimately, the majority of this research was low quality with a high risk of bias, and a meta-analysis of 78 studies in 2020 concluded that actually, the opposite may be true. Reduced exercise performance was observed in the early follicular phase, not the expected reduction during luteal phase. Even then, the effect sizes were deemed trivial. There simply isn’t’ enough evidence to suggest any way of loading training to maximise performance or body composition changes at this point.

Many people forget too that the differences between cycles for one person who menstruates can be huge. Some months a period can be almost easy to ignore, whilst others, our boobs are sore for weeks and for 5-7 days, we’re more exhausted than that one time we stayed out past 4am in our 30s.

The answer? Do what’s right for you and your clients. I give the people I work with the opportunity to autoregulate deloads, which is particularly helpful for those who struggle most with PMS symptoms.

What about oral contraceptives? Do they impact our muscle?

Much like the evidence surrounding the menstrual cycle, data is variable here.

Mechanistically, because of the impact of exogenous hormones (and their subsequent impact on our own circulating endogenous hormones), it’s plausible to speculate that there may be some impact of hormonal contraceptives on strength, hypertrophy and lean mass with resistance training.

A recent study took untrained women through 10 weeks of resistance training, half of them were taking the oral contraceptive, half weren’t. At the end of the 10 weeks, there was no difference in strength or hypertrophy and in fact, those using oral contraceptives tended to have larger increases in lean body mass compared with those who didn’t (not quite aligned with the current TikTok narrative that oral contraceptives stop muscle gain.

A meta-analysis of 42 studies in 2020 highlighted that the probability of a small effect on performance favouring naturally menstruating women was moderate to small, and whilst oral contraceptive use might result in slightly inferior exercise performance vs. without, any group effects are trivial and highly variable. Simply, we don’t have evidence to suggest that oral contraceptives impact training performance, strength or lean mass.

A side note to this is that there is some evidence that oral contraceptives minimise the strength fluctuations across the cycle that some people experience as per the above, which may aid in more effective training throughout the month. Some people take the pill to manage debilitating PMS symptoms which again, hinder training performance. Others take it to avoid pregnancy, which shockingly again, may hinder training performance.

If the pill is helpful for you or your clients, there’s no reason to avoid it when it comes to your training.

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I teach all of this in more detail on EIQ Nutrition, for personal trainers looking to upskill their knowledge with practical evidence-based nutrition, or anyone looking to simply learn for themselves.

With a wealth of misinformation about this topic on social media, let’s talk about how your hormones impact your training and muscle gain. But first, take a glance at what happens with our key reproductive hormones across the menstrual cycle.

Our cycle can be split into 2 key phases, the follicular phase (first 1-14 days on average, before ovulation), and the luteal phase (next 15-28 days on average, after ovulation). Ovulation occurs on average on day 14 of a 28 day cycle, but many people who menstruate will experience variations in their cycles from average, and month-to-month. Day one of menses signals day one of a cycle.