Women’s Hormones and Running
Jason Karp, Ph.D.
While a man’s hormonal environment is pretty stable, a woman’s hormonal environment is constantly changing. The physiological changes resulting from menstrual cycle-induced fluctuations in estrogen and progesterone are exacerbated during exercise, especially if it’s intense.
Body temperature changes rhythmically throughout the menstrual cycle, peaking during the luteal phase in response to the surge in progesterone. Progesterone acts on the brain’s hypothalamus (the temperature control center), which increases set-point temperature. A higher body temperature increases the threshold for dissipation of heat. In other words, a woman’s body must reach a higher temperature before her thermostat compensates and begins to cool itself. Not a good thing when you’re running on a hot and humid day, as you want to begin the cooling response as soon as you can. Estrogen has the opposite effect on the hypothalamus, decreasing body temperature, which explains why body temperature is lower during the estrogen-dominant follicular phase.
Metabolism and Muscle Glycogen
Under the influence of estrogen, women rely more on fat than men when running at the same pace, which gives women an advantage during very long endurance activities, like ultramarathons.
Progesterone stimulates ventilation independent of the intensity of a run, which can increase a runner’s perception of effort since runners typically link their perception of effort to how much they’re breathing. Breathing is greater during the luteal phase, when progesterone concentration is highest. Thus, a female runner may feel more winded during her luteal phase workouts compared to her follicular phase workouts.
Lung function after exercise is also affected by the phase of the menstrual cycle, with women having more trouble breathing during the luteal phase. This has huge implications for runners with asthma, since exercise is a powerful trigger of asthma symptoms. Thus, the declining lung function in the luteal phase can negatively impact training and competition strategies in an asthmatic runner. Females with asthma experience a worsening of asthma symptoms and increased bronchodilator use during the mid-luteal phase. Interestingly, lung function and asthma symptoms seem to vary cyclically. Thirty-three to 52 percent of asthmatic women report a premenstrual worsening of asthma symptoms, and an additional 22 percent report that their asthma is worse during their periods.
The most important determinant of bone density in women is the circulating concentration of estrogen. Any condition that reduces estrogen concentration negatively affects bone remodeling, which explains why a woman’s risk for osteoporosis and fractures increases dramatically with menstrual irregularities or absent menstrual cycles (amenorrhea) and after menopause, when there is a lack of estrogen. Indeed, estrogen deficiency caused by amenorrhea is the most significant risk factor for osteoporosis in active women. If you run a lot and have a low body fat percentage and have menstrual irregularities, you need to do other things to keep your bones healthy, including adequate intake of calcium and vitamin D, strength training and, possibly, oral contraceptives, which supply you with estrogen.
As a female runner, you can expect to perform better during times of the menstrual cycle when estrogen is the dominant hormone and perform the worst when progesterone is the dominant hormone. Many of the female runners I’ve coached have experienced their worst training days in the few days leading up to and including menstruation. You may find that, while harder workouts may be more challenging during your period, easy running may actually improve your mood and alleviate physical symptoms associated with your period.
Avoid challenging workouts around menses, especially if you don’t feel well at that time or if you feel bloated due to the rapid drop in progesterone as you transition from the luteal phase to the follicular phase. For example, if you have a 28-day cycle starting on Monday, and menses occurs on days 1 to 3 (Monday to Wednesday), plan your hard workout on Thursday or Friday that week. If you have two workouts planned, schedule them on Thursday and Saturday, or schedule just one workout the week of menses and two workouts during the other three weeks of your cycle. If menses lasts five days (Monday to Friday), schedule one workout the week of menses and two workouts during the other three weeks of your cycle.
Dr. Jason Karp is a nationally-recognized running and fitness expert, 2011 IDEA Personal Trainer of the Year, and owner of RunCoachJason.com. He holds a Ph.D. in exercise physiology. He writes for international running, coaching, and fitness magazines, is the author of five books, and is a frequent presenter at national fitness and coaching conferences. To order a signed copy of Running for Women, go to http://www.runcoachjason.com/merchandise.
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