Women’s hormones and cycles are very sensitive and very complex to understand. Many high intensity or endurance athletes (but not all) will experience irregular or total loss of menstruation which can bring with it consequences to bone density, injury risk, and compromised fertility. Regarding athletic performance through a women’s cycle, a systematic review published in Sports Medicine by McNulty et al 2020 found only “trivial” reduction in athletic performance during the follicular phase with more information needed to make any recommendations on the subject. While a woman’s cycle doesn’t appear to affect her athletic performance, her athletic performance could affect her cycle.
First, let’s break down the phases of a menstrual cycle:
Days 1-14, the follicular phase– this phase begins on the first day of bleeding (period) and continues through to ovulation. Key in this phase is the rise of estrogen
Ovulation– the point that estrogen peaks
Days 15-28, the luteal phase– from ovulation until bleeding (period). Key in this phase is the decrease in estrogen and the rise of progesterone.
Realize, a majority of women in our country do not present with exact 28 day cycles and that can still be normal. While the days may vary, one can use the distinguishing events of period and ovulation to determine what phase of their cycle they are in.
Hormone review in relation to this discussion:
Progesterone- an increase in progesterone triggers the onset of a period or if a fertilized egg is present, progesterone is essential for maintaining a pregnancy
Estrogen- it has been shown that this hormone improves our ability to recover from training and has a protective function against muscle damage
Exercise has been shown to affect our hormone levels in a few ways. Regular exercise has been shown to reduce estrogen levels by 18.9% and progesterone levels by 23.7%. These decreases are found to be most pronounced during the luteal phase of a cycle. Of note, progesterone is more sensitive to body stress than estrogen. Additionally, higher intensity exercise has been shown to decrease progesterone specifically. How this works is that the prolonged stress of higher intensity exercise increases cortisol (the body’s stress hormone). To create this extra cortisol, the body will “steal” progesterone to convert it to cortisol, and thus lower progesterone levels. Now remember, our bodies need sufficient progesterone during that luteal phase in order to signal a period or maintain a pregnancy, so high intensity exercise during that phase could alter our natural progesterone production.
So how to workout revolving around your cycle?
It has been proposed that tapering down exercise intensity during the luteal phase will help prevent the negative effect high intensity exercise could have on your progesterone levels. What this looks like for your workouts:
Day 1 of bleeding, so from the onset of your period until about day 14 or ovulation: This is the time to take advantage of higher energy levels and the protective effects of estrogen. Focus on high intensity interval training (HIIT), cycling, running, weight lifting, crossfit, swimming, any other high intensity or endurance workout
After ovulation until the start next period, especially toward the end, about day 20-28: This is the time to taper down intensity and endurance of exercise and focus on things like yoga, walking, swimming, and lower intensity exercise or weight lifting
Realize, this is not to say women MUST take it easy for the entire last week of their cycle. That is not doable for any professional or competitive athlete or for some people’s work out preferences. The bigger takeaway is to aim for your hardest and longest workouts to be in the first few weeks of your cycle, especially if hormone stasis and fertility is your goal.
Kossman DA, Williams NI, Domchek SM, Kurzer MS, Stopfer JE, Schmitz KH. Exercise lowers estrogen and progesterone levels in premenopausal women at high risk of breast cancer. J Appl Physiol (1985). 2011;111(6):1687-1693. doi:10.1152/japplphysiol.00319.2011
Janse de Jonge X. Effects of the Menstrual Cycle on Exercise Performance. Sports Medicine. 2003;33(11):833-851.