Controversy surrounds the role of exercise in the development of menstrual problems. Researchers have noted that more female athletes have amenorrhea, prolonged cycles, or delayed menstrual onset than do other women, but there is no general agreement on the reasons.

According to one theory, the lack of menstruation among athletic women stems from loss of weight and body fat. Glandular problems have also been blamed. Low estrogen levels, vitamin deficiency, and the stress of rigorous training and competition are other proposed causes.

On the positive side, many athletes do have regular menstrual cycles — and they have milder cramps, less PMS, shorter-lasting periods, and fewer headaches than their sedentary sisters. On balance, most doctors recommend regular, reasonable exercise.