Effects of short-term strenuous endurance exercise upon corpus luteum function

Purpose: The present study tested whether short-term, abruptly initiated tr aining can cause corpus luteum dysfunction when exercise is limited to eith er the follicular or luteal phase of the cycle. Methods: Reproductive hormo ne excretion and menstrual characteristics were studied in sedentary women who exercised only during the follicular (N = 5) or the luteal (N = 4) phas e. Six women served as controls, three of whom exercised at a low volume an d three who remained sedentary. Weekly progressive increments in exercise v olume continued until either ovulation (follicular group) or menses (luteal group) occurred. Physical activity and nutrient intake were closely monito red with the intent to maintain body weight. Results: No luteal phase distu rbances 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 th e proportion of cycles disrupted in control subjects (P < 0.05). Conclusion s: These results suggest that exposure to abrupt onset of training can alte r luteal function, regardless of the menstrual cycle phase in which exercis e occurs. This study also demonstrates that a relatively low volume of exer cise suffices to induce mild disturbances in luteal function.