Hormonal Responses to Exercise in Non-Athletic Women

Women who had a history of regular menstrual cycles and who had not participated in a regular exercise or sports program for at least six months were recruited for a study of the effects of initiation of an exercise program on ovulation. After a control menstrual cycle during which basal hormone levels and the occurrence of ovulation were assessed, exercise on a treadmill was begun on the first day of the second menstrual cycle; exercise was continued at 85% of maximum heart rate for three sessions per week of from 15 to 30 minutes. The effect of this program on ovulation, luteal function, and on levels of Cortisol, testosterone, prolactin and growth hormone measured 10 minutes after cessation of exercise was studied during the month of exercise and at the same times of day in pre- and postexercise control months. Initiation of the exercise program resulted in a shortening of the follicular phase of the menstrual cycle with no effect on luteal phase length or on progesterone levels or pregnanediol excretion during the luteal phase. Testosterone and growth hormone were significantly elevated after exercise by comparison with values obtained during the control months, but Cortisol and prolactin were not. Cortisol levels may have been measured too soon after exercise began to detect an elevation. However, the complete absence of a prolactin elevation may be the reason for the failure of the brief exposure to exercise of this intensity to affect ovulation.