Nieman, David C. Dr.PH., FACSM
David C. Nieman, Dr.PH, FACSM, is professor and director of the Human Performance Laboratory, Appalachian State University, in Boone, North Carolina, an active researcher, and author of several textbooks on health and fitness.
Q: My daughter is in college and runs, swims, or cycles for at least two hours a day in preparation for triathlon events. I am worried that this amount of exercise is too much, especially because she has become quite thin. Can high levels of exercise be harmful to women?
A: Yes, for some female athletes, the pressure to keep body weight low and to be successful can lead to heavy training and disordered eating, loss of menstrual periods, and thinning of the bones. This syndrome is called the female athlete triad (1-5).
It wasn't long ago that women were thought to be too fragile to compete. Women were first allowed to participate in the Olympics in 1912, and some events such as the women's marathon were only added in 1984. [ACSM contributed significantly to that decision through its landmark Opinion Statement, "The Participation of the Female Athlete in Long-Distance Running" published in 1979.] At the end of the 800-meter race in the 1928 Olympics, The New York Times reported, "The cinder track was strewn with wretched damsels in agonized distress." No women's race longer than 200 meters was held until 32 years later.
Today, more and more sports are available to women, and there is a push worldwide to ensure equity for women in sports. This movement began in 1972 when President Richard Nixon signed into law Title IX, the federal legislation mandating equal opportunities for collegiate female athletes. And women are proving that they are capable of feats once thought impossible for the "weaker sex." At the 1984 Olympic Games in Los Angeles, Joan Benoit won the gold medal in the first ever Olympic marathon race event for women. Her time was 2 hours and 24 minutes, a standard that would have won 11 of the previous 20 men's Olympic marathons. In 1988, Paula Newby-Fraser completed the Hawaiian Ironman Triathlon (2.4-mile sea swim, 112-mile cycle ride, and a 26.2-mile run), in 9 hours and 1 minute, just 30 minutes or 6% slower than the male winner. Only 10 men were ahead of her that year.
The gap between the best men and women athletes has shrunk sharply during the past 25 years. In the Boston Marathon, for example, the difference in winning times for men and women has diminished from 54 minutes in 1972 to about 14 minutes during recent races. However, the gender performance gap in many endurance events has now stabilized, largely because the quick gains following the loosening of social restraints have run their course.
More women are exercising today than ever before. Once deemed socially unacceptable, women now engage in strenuous recreational and competitive physical activities. Women of the 1960s were concerned about the stigma of getting big muscles from exercise and whether their femininity would be marred. Today, interests center on the same fitness and performance issues that concern men.
Despite these trends, the best national surveys still show that more women than men are physically sedentary. Men are more likely than women to engage in vigorous physical activity and muscle-strengthening activities like weight training. There still is much more room for progress, and research is needed to more clearly define how the genders differ in their responses to exercise training.
For some women, the pressure to succeed in competitive sports has led them to train heavily while eating less than recommended to achieve low body weights and high performance levels. Although all physically active girls and women are potentially at risk for the female athlete triad, it is more prevalent in sports that are subjectively scored (dance), endurance sports emphasizing a low body weight (distance running), sports requiring revealing clothing for competition (swimming), sports using weight categories (wrestling), and sports emphasizing a prepubertal body type for success (gymnastics) (1, 2, 4). Under these stresses, some women may lose their menstrual periods, a condition termed amenorrhea. If amenorrhea is experienced long enough, estrogen levels may decrease, leading to loss of bone mineral mass and early osteoporosis.
Typically, only approximately 2% to 5% of the female population has amenorrhea. This proportion, however, can climb to 50% in some athletic groups, especially female runners and ballet dancers. Close to half of female runners who train 80 or more miles a week are amenorrheic, compared with only 5% to 10% of runners who are moderate in their training. In female athletes with amenorrhea, the density of bones is 20% to 30% lower than normal, and risk of stress fractures in the bones of the legs and feet is high (3-5).
It appears that heavy amounts of exercise can actually disrupt the release of certain hormones from the brain that are needed by the ovaries to go through a normal and full cycle (3, 5). Also, when the female athlete does not eat enough, the body goes into semi-starvation mode, interrupting the normal release of hormones that drive the menstrual cycle.
Although the percentage of athletic women who eat poorly is not known for certain, estimates from experts range from 30% to 65% (1-5). With the disruption in menstrual periods, estrogen levels drop to levels experienced by women after menopause, leading to a rapid loss of bone mass.
All women who stop menstruating or menstruate irregularly because of their exercise program are urged to see a doctor, start eating more while exercising less, increase calcium intake to 1,500 mg a day, and, in some cases, receive estrogen replacement therapy. With these changes, the menstrual period often returns, and bone mass is built back up to near normal levels for many but not all female athletes (1, 2).
1. Ireland, M.L., and S.M. Ott. Special concerns of the female athlete. Clinical Sports Medicine
2. Kazis, K., and E. Iglesias. The female athlete triad. Adolescent Medicine
3. Warren, M.P., and L.R. Goodman. Exercise-induced endocrine pathologies. Journal of Endocrinology Investigation
4. Birch, K. Female athlete triad. British Medical Journal
5. De Souza, M.J. Menstrual disturbances in athletes: A focus on luteal phase defects. Medicine & Science in Sports & Exercise®