Effects of short-term strenuous endurance exercise upon corpus luteum function. Med. Sci. Sports Exerc., Vol. 31, No. 7, pp. 949-958, 1999.
Purpose: The present study tested whether short-term, abruptly initiated training can cause corpus luteum dysfunction when exercise is limited to either the follicular or luteal phase of the cycle.
Methods: Reproductive hormone excretion and menstrual characteristics were studied in sedentary women who exercised only during the follicular (N = 5) or the luteal (N = 4) phase. Six women served as controls, three of whom exercised at a low volume and three who remained sedentary. Weekly progressive increments in exercise volume continued until either ovulation (follicular group) or menses (luteal group) occurred. Physical activity and nutrient intake were closely monitored with the intent to maintain body weight.
Results: No luteal phase disturbances occurred in any of the control subjects, whereas 40% of follicular and 50% of luteal exercisers experienced luteal defects. The proportion of menstrual cycles disrupted was not different between luteal and follicular exercisers (50% vs 30%, respectively) but was significantly greater than the proportion of cycles disrupted in control subjects (P < 0.05).
Conclusions: These results suggest that exposure to abrupt onset of training can alter luteal function, regardless of the menstrual cycle phase in which exercise occurs. This study also demonstrates that a relatively low volume of exercise suffices to induce mild disturbances in luteal function.