Some studies do attempt to overcome this by using less-invasive and cost-effective methods such as:

1. Urinary ovulation predictor tests: these work by identifying the surge in luteinising hormone (LH) that triggers ovulation and are actually pretty accurate (97%) (9). Obviously testing body fluids can be quite expensive, time-consuming and sometimes invasive for the study participants so it is very rarely done.

2. Basal body temperature: We can also use Basal body temperature (BBT) which increases by ~ 0.3 C (0.5-1 F) in luteal phase & remains elevated until menstruation. This is an indication that ovulation has occurred but its accuracy is roughly 22% because BBT is influenced by many factors (illness, alcohol, stress - even wake time) (9). Checking changes to cervical mucus is actually a more accurate method of determining ovulation.

3. Calendar-based methods: When using calendar-based methods,’ we should really be looking at 3-6 month averages, even before study enrolment, to better understand what someones “normal” is. It’s important to point out that even if menstruation (the period) occurs, that does not guarantee ovulation has occurred.

Author recommendations

In sum, the available reviews and meta-analyses suggest that menstrual cycle phase has a limited effect on strength performance and emphasises the influence of low-quality studies with poor methodological quality on which to base firm conclusions.

The authors recommend that right now;

• Programmes should be tailored to the individual, not based on the menstrual cycle phase until we have higher-quality evidence 

• Menstrual cycle should be considered as a potential influencing factor (alongside sleep, stress, nutrition etc) when designing a resistance training programme

This to me is largely positive and sets us free from this narrative of our sex hormones dictating BUT what none of these reviews have considered is the perceived effect and symptoms and I think this is KEY = yes our sex hormones might not be influencing our performance directly BUT they might be having indirect effects that might influence our performance.

My takeaway

If you’ve read my book The Female Factor or have followed my work for the last few years, you will know by now that I am incredibly passionate about understanding how the menstrual cycle influences our strength, energy, and performance and how we can use this information to influence our training and recovery. However, my overarching message remains the same, the recommendations from the limited research we have may guide us, but shouldn’t be seen as the rule and the most important piece of evidence comes from collecting data from your own menstrual cycle and understanding how that affects your training and recovery.

Is this a bad thing? No, it can be largely positive and sets us free from this narrative of our sex hormones dictating how strong we are or how well we perform BUT what none of these reviews have considered is the perceived effect and how menstrual symptoms affect us, which I think this is KEY. Yes our sex hormones might not be influencing our performance directly BUT they might be having indirect effects that might influence our performance.

As someone who menstruates, I find this practice incredibly empowering and helpful to guide my training - and lifestyle in general. However, no two people are the same - no two cycles are the same - and not everyone will experience significant changes in strength performance across their cycle and/or improved strength adaptation with phase-based training.

But that does not mean that differences do not exist, and the absence of (good quality) evidence is not evidence of absence.

So I echo what those authors conclude and I call for more evidence and I also urge you not to disregard the menstrual cycle as a potential influencing factor (alongside sleep, stress, nutrition, etc.) when it comes to how we perform inside and outside of the gym.