Muscles and hormones: What every woman should know

New research suggests we may have been giving hormones more responsibility for muscle growth than the evidence supports.

After decades of exercise research being conducted predominantly on men, the past few years have seen a welcome shift towards understanding how female physiology influences performance and health. Menstrual cycles, menopause, and hormonal health have (and rightly so) become central to conversations around exercise science.

But as the research evolves, so do wellness marketing strategies. Social media has transformed nuanced findings into definitive rules, spawning a growing market of cycle-syncing workout plans, hormone-specific training programmes, and claims that women should only build muscle during certain phases of their menstrual cycle. If you haven’t been bombarded with conflicting messaging on how to approach self-care and exercise on your period or in different phases, then lucky you. It feels as though everyone has different opinions on an objective subject.

But a major new study is now challenging these confusing assumptions. Published this month, the research found that the natural hormonal fluctuations experienced across the menstrual cycle appear to have little influence on how much muscle women gain from resistance training. In other words, women can build strength and muscle regardless of where they are in their cycle, suggesting that sex hormones may play a smaller role in muscle adaptation than previously believed.

The findings don't suggest hormones are unimportant, though. But they do challenge the increasingly popular narrative that they dictate every aspect of physical performance. Hormones such as oestrogen and progesterone remain fundamental to bone health, metabolism, reproductive health, and many aspects of recovery. Life stages including pregnancy, perimenopause, and menopause are all associated with genuine physiological changes that deserve way more targeted research and personalised support.

If we focus on the findings of this study, we can see whether the hormonal changes that occur during a typical menstrual cycle alter the body's ability to respond to strength training. This matters because women's health has historically swung between two extremes. For decades, female physiology was overlooked entirely, with training recommendations often extracted from studies involving male participants. More recently, the pendulum has shifted in the opposite direction, with hormones positioned as the explanation for almost every difference in female performance. But it’s a lot more complex than that for women, and always has been.

Muscle growth is influenced by multiple factors. Progressive overload, adequate dietary protein, total energy intake, sleep quality, recovery, and training consistency, to name a few. Hormones contribute to that picture, but they are unlikely to override those fundamentals on a week-to-week/ phase-to-phase basis.

But there is a risk: oversimplifying hormonal science. Looking at all this, it is easy to be discouraged. A lot of women online subscribe to the idea that there are certain optimal weeks to train, or that exercising during the wrong phase of their cycle is somehow ineffective or will worsen symptoms.

This research advocates for a personalised approach for women. Some of us may notice fluctuations in energy, motivation, or symptoms throughout our cycle and choose to adjust training accordingly. Others may experience little difference at all. Both experiences are valid!

So yes, it is an important finding that hormones have little effect on muscle growth, but it is also revolutionary in that women’s health research is becoming more sophisticated. Better research means moving beyond broad generalisations that were originally targeted to the male body and towards guidance that reflects individual experiences rather than popular trends.