The first thing you need to know is that athletes have performed successfully at the highest levels during all phases of the menstrual cycle. Measurable differences are extremely minor—at least at the elite level. This means that the practical side of training on your period has less to do with what you can do and more to do with a few subjective factors.
Practically speaking, there are three things that can have a impact on performance during your period:
Your body temperature probably increases by 0.3 to 0.5º C around the time of ovulation. This is due to a drop in estradiol and an increase in progesterone. Body temperature begins to decrease again around the start of menses.
Increased body temperature can increase the perceived difficulty of exercise. Our personal trainers have also noticed that elevated body temperature can decrease the perceived effectiveness of rest. This is due to a higher breathing rate—and the signals this relays to your nervous system about fatigue. This is particularly relevant in hotter and more humid environments. We know how muggy Toronto can get in the summer.
Some women will experience lowered hemoglobin levels during menstruation. This can affect energy levels—particularly when iron is low in general. This is worth getting confirmed with a standard blood test.
Nutrition tip: if you hate taking an iron supplement, using iron cookware or this bad boy can help.
Many women report lethargy, lowered motivation, and lowered concentration during menses. Consider being a little more conservative with injury risk during this time. That may relate to learning new skills or avoiding exercises with a narrow bandwidth for safe execution.
Nutrition tip: there is evidence that zinc, magnesium, and fish oil can alleviate symptoms of PMS. More detail available on examine.com.
Another common (but not universal) experience is cravings. There is often a psychological cost to restriction. So, rather than give you useless advice like, “Try to eat less,” we instead have three recommendations:
- If you’re eating a certain food solely because it tastes good, then make sure you’re really tasting it! Eat slowly. Enjoy it.
- When practical, start with protein and nutrient-rich foods before moving onto other fare.
- Tracking your body temperature (first thing every morning—before getting out of bed) can give you more insight into your experience. When you see your body temperature increasing, it’s a signal that you will need more calories and may also experience cravings. Knowing this ahead of time can help you contextualize what you’re feeling.
While your theoretical performance is fundamentally unchanged, your practical performance may be—primarily due to increased perception of difficulty and lowered mood and energy. You may want to err on the side of caution with exercise selection and intensity during these times.
For more information on the subject, Girls Gone Strong provide some excellent resources.