RUNNING INDUCES MENSTRUAL DISTURBANCES BUT BONE MASS IS UNAFFECTED, EXCEPT IN AMENORRHEIC WOMEN

PURPOSE: To investigate the prevalence of exercise-related menstrual a nd sex hormonal disturbances and the effect of exercise on bone mass a nd metabolism in female runners at various training levels. SUBJECTS A ND METHODS: Two hundred five premenopausal women (running 0 to 140 km a week) were recruited from a large population of female runners who h ad responded to a questionnaire regarding exercise habits. Maximum oxy gen uptake was determined by treadmill testing. Gynecologic status was assessed on entries in a menstrual calendar and by transvaginal ultra sonography; sex hormonal status was measured three times with 10-day i ntervals. Bone mass was measured in the lumbar spine, proximal femurs, and total body by dual-energy x-ray absorptiometry, and in the forear m by single-photon absorptiometry. Bone turnover was assessed by measu rement of plasma osteocalcin, serum alkaline phosphatase, and urinary calcium and hydroxyproline. RESULTS: Sex hormonal disturbances were si gnificantly related to training intensity. Compared with the normally active women, the baseline levels and fluctuations of estradiol and pr ogesterone in the elite runners were reduced by up to 25% to 44% (0.01 < p <0.05). The prevalence of amenorrhea increased from 1 % in the nor mally active subjects to 11 % in the elite runners. No statistically s ignificant relation was found between running activity and bone minera l measurements or bone turnover. However, the group of amenorrheic run ners had a 10% reduction in lumbar bone density as compared with the n ormally menstruating runners (p <0.05), but the bone turnover was simi lar. CONCLUSION: In the large majority of the female runners, no skele tal affection was found despite significant sex hormonal and menstrual disturbances. Only the runners with amenorrhea might be at increased risk of osteoporosis.