Induction of Menstrual Disorders by Strenuous Exercise in Untrained Women

We performed a prospective study of 28 initially untrained college women with documented ovulation and luteal adequacy to determine whether strenuous exercise spanning two menstrual cycles would induce menstrual disorders. To ascertain the influence, if any, that weight loss might exert, we randomly assigned the subjects to weight-loss and weight-maintenance groups. Subjects were expected to run 4 miles (6.4 km) per day, progressing to 10 miles (16.1 km) per day by the fifth week, and to engage daily in 3 1/2 hours of moderate-intensity sports. The normalcy of the menstrual cycles during the period of exercise was judged independently according to clinical and hormonal criteria, the latter comprising serial measurements of gonadotropin and sex-steroid excretion. A higher percentage of abnormalities proved to be detectable by hormonal means (P