Your circadian rhythm is a 24 hour hormonal cycle that prepares the body for activity, sleep, concentration, when to eat. The general way it works is: energy, focus, and drive is highest in the morning when testosterone and cortisol is higher, with this slowly waning throughout the day. Ability and desire to communicate or socialise increases throughout the day, peaking in the afternoon. Then energy levels reduce in the evening, encouraging relaxation to prepare the body for sleep.
The circadian rhythm is influenced by exposure to light and dark, so it generally operates in sync with the sun. The circadian rhythm can be interrupted by things like changing time zones, shift work, and exposure to artificial light at night (which is a big reason why we shouldn’t be on our phones at night!).
While we all have a circadian rhythm, people with female physiology also experience another biological timekeeper – a monthly infradian rhythm in the form of the menstrual cycle. There are hormonal changes occurring throughout the monthly cycle that affect their brain, metabolism, immune system, microbiome, stress response, and reproduction.
A lot of our daily living is set up around the circadian rhythm, including work hours, recommended training times and intensities, when and what to eat, and when is the best time to have sex. However, this primarily favours those with male physiology as their hormonal processes are consistent day to day. On the other hand, people with a menstrual cycle are also influenced by their infradian rhythm and have hormonal fluctuations over a monthly cycle.
Most training and nutrition plans are designed based on the circadian rhythm because this is simple, in that it only needs to account for energy and hormonal fluctuations over a 24 hour period. It means that training and nutrition plans can be pretty straightforward and can be pretty much the same all the time.
However, this is not optimal for 50% of the population.
At different points throughout the monthly cycle, energy levels and focus will vary, as will calorie requirements. Therefore, training and nutrition should change throughout the month to support this and to get the most out of each phase of the cycle.
The same way training is often programmed throughout the week to balance out heavy and light days, and to manage recovery, this could be done over a monthly cycle as well, where certain areas of training are pushed at different parts of the month.
This won’t be the same for each person with a monthly cycle so it can be a bit challenging and require more individualisation (which is why this won’t happen on mass produced training and nutrition programs). But if these hormonal fluctuations were harnessed and worked with, instead of against, the training outcomes for this section of the population could be significantly improved.