The frequency of your visits to the gym may seem to have little to do with your menstrual period, but these events are closely linked. Menstruation is a biological process controlled by your body's production and regulation of multiple hormones. Exercising places physical demands on your body that can affect your hormone levels -- and menstrual cycle -- in different ways.
Generally lasting three to five days, your menstrual period or menstruation is the portion of your menstrual cycle during which your body sheds blood and uterine tissue. The first day of your menstrual period marks the first day of your menstrual cycle, which typically lasts 28 to 32 days for most women. During the first half of your menstrual cycle, your body's levels of the hormone estrogen increase; this hormone boost causes the uterine lining to thicken in preparation for pregnancy. Additional hormone fluctuations cause one of your ovaries to release an egg, which travels to the uterus for fertilization. If fertilization doesn't occur, your hormone levels drop, the egg disintegrates and you undergo menstruation.
Moderate physical activity may actually improve various severe side effects of menstruation -- including uterine cramping, vomiting, nausea and back pain -- that occur in approximately 50 percent of women, according to Dr. Thomas Hyde, sports chiropractic physician and co-author of "Conservative Management of Sports Injuries." These menstrual symptoms most likely develop when the uterine lining releases prostaglandins, hormones that limit blood flow to your uterus and cause painful uterine contractions. When you exercise, your body increases blood flow to the uterus and boosts its production of endorphins, "feel-good" hormones that may counter the effects of these pain-inducing prostaglandins in some women.
Intense physical activity combined with decreased caloric intake may cause your menstrual period to cease. This condition, called amenorrhea, occurs most frequently in female distance runners, but it also may develop in women who participate in other sports that emphasize slenderness, like ballet, gymnastics and figure skating. Women who develop amenorrhea experience an ongoing energy deficit, which eventually causes the hypothalamus -- your brain's control center -- to suppress the release of hormones that regulate ovarian function. The ovaries fail to release an egg for fertilization, which keeps you from experiencing a menstrual period.
Talk to your doctor if you're concerned that you're experiencing menstrual irregularities including skipped periods because of exercising. Prolonged amenorrhea may lead to the loss of calcium from your bones, which arises from decreased estrogen levels in your body. Over time, this can contribute to bone-mass loss and the development of osteoporosis and fractured or broken bones. Treatment for amenorrhea typically includes an increase in caloric intake and a decrease in physical activity.
- The National Women’s Health Information Center: Menstruation and the Menstrual Cycle
- “Human Reproductive Biology”; Dr. Richard Jones et al.; 2006
- “Conservative Management of Sports Injuries”; Dr. Thomas Hyde et al.; 2007
- “Women’s Sports Medicine and Rehabilitation”; Dr. Nadya Swedan; 2001
- “Amenorrhea”; Dr. Nanette Santoro et al.; 2010
- “A Gynecologist’s Second Opinion”; Dr. William Parker et al.; 2003