I’m type A (aren’t all runners?!), so I track a lot of things in my life. The amount of miles I run, the number of books I read and, for about a year now, my fertility.
Tracking my fertility along with my running has made me really interested in how my cycles affect my running performance. I have learned quite a lot about the menstrual cycle over the years and how that affects a woman’s body in general. In my perspective, here is why a woman would want to keep track of her cycle in order to train more effectively.
I’ll try not to bring back terrifying flashbacks from your eighth grade health and science class, but we do need to do a little review of the hormones related to the menstrual cycle. Bear with me, okay?
The hypothalamus releases a hormone known as the Gonadotropin Releasing Hormone (GnRH). GnRH stimulates two other hormones in the anterior pituitary called the Follicle Stimulating Hormone (FSH) and the Luteinizing Hormone (LH). The former is responsible for follicular growth. The latter is responsible for follicular growth and ovulation.
Finally, a woman’s ovaries contain estrogen and progesterone. The former matures follicles and stimulates the endometrium. The latter differentiates the endometrium.
The entire duration of a menstrual cycle can be divided into four main phases: the menstrual phase, the follicular phase, the ovulation phase and the luteal phase.
The follicular phase is the first part of the menstrual cycle and lasts anywhere from 10 to 17 days. During this time, GnRH stimulates production of FSH and LH. FSH stimulates proliferation of granulosa cells in the ovaries. Granulosa cells produce estradiol, and one follicle becomes dominant.
During the ovulation phase, there is a critical peak of estradiol for 2-3 days, about 24 hours prior to ovulation. This estradiol peak causes a LH surge, and the sustained levels of estrogen further suppress FSH. 32 to 44 hours after the onset of the LH surge, and 10 to 12 hours after the LH level peaks, the muscle fibers of the fallopian tube contract and transport a fully matured egg.
In the luteal phase, a corpus luteum develops from the ruptured follicle. Progesterone peaks 5 to 7 days after ovulation, which leads to an increase in body temperature and suppresses stimulation of new follicles. This causes the endometrial lining to change, which leads to menstruation.
How this affects your running
Still confused? I’ll do my best to bring it down to a more practical level now.
Female runners can expect to perform better during times of the menstrual cycle when estrogen is the dominant hormone. That’s during the follicular phase. This is because estrogen accelerates your metabolism and increases your fat storage, so your endurance is improved during this time. Your body relies more on the fat in your system than the carbohydrates at this time, so it might take you longer to get tired. Plus, the estrogen makes it easier for you to get stronger – so get plenty of strength training in during this time of your cycle!
Female runners can expect to perform worst when progesterone is the dominant hormone. That’s the luteal phase. The surge in progesterone during the luteal phase of your menstrual cycle increases body temperature. Not a good thing when you’re running on a hot and humid day. Progesterone also stimulates breathing, so you may feel more winded during your luteal phase workouts compared to your follicular phase workouts.
As for your period itself? A woman can expect to lose an average of 20 to 80ml of blood in the 4-5 days of menstruation. Hemoglobin concentration may decrease because of that, which can negatively impact your ability to transport oxygen in your blood. You may need to supplement your normal diet with iron at this time.
I took a poll on my Instagram to ask how a cycle affected my female followers’ workouts. Here’s what some of them had to say.
“Right before and the day after [my period] starts, I end up feeling too tired and bloated to go running – but then I remember the negative perception society has of women whilst on their cycle, and I force myself to go anyway.”
“I’m more likely to need super frequent breaks in hot yoga when I am within a few days of my period starting because I feel light-headed more quickly even if I up my water intake significantly. I also don’t sleep well around that time which similarly makes working out hard.”
“The struggle is real. I feel sluggish and off when I’m starting my cycle. Midway I feel great.”
Do you track your cycle? Do you notice how it affects your performance?