BONE-DENSITY AND CYCLIC OVARIAN-FUNCTION IN TRAINED RUNNERS AND ACTIVE CONTROLS

This study was conducted to determine whether rigorous exercise traini ng adversely affects ovarian hormone levels and bone health in cyclica lly menstruating trained runners. Ovarian hormones, bone mineral densi ty (BMD), body composition, 3-d diet records, 3-d estimated energy exp enditure, and menstrual histories were evaluated in 10 trained collegi ate runners and 10 moderately active controls. The trained runners had lower total body calcium per kg of soft lean tissue measured by DEXA (P = 0.045). Half of the trained runners had experienced stress fractu res compared with only one of the moderately active controls. The trai ned runners' lumbar (L2-L4) BMD (1.178 g . cm(-2)) was not significant ly different from that of the active controls (1.283 g . cm(-2)) (P = 0.074) but, for all subjects combined, there was a significant inverse relation between L2-L4 BMD and distance run per week (P = 0.036). Fur ther, adding age, body weight, percent body fat, daily energy intake, and daily calcium intake to a stepwise multiple regression analysis di d not significantly improve predictive precision. The trained runners consumed nearly twice the amount of calcium (1089 mg . d(-1) vs 641 mg . d(-1), respectively; P = 0.036), while intake of other nutrients di d not differ significantly between groups. Urinary estrone conjugates (E1C) were lower in the trained runners during the early follicular ph ase (P = 0.028), while pregnanediol-3-glucuronide (PdG) was not signif icantly different between groups during the luteal phase (P = 0.213). Thus, it appears that lower estrogen production, especially during the early follicular phase, and not progesterone, is associated with lowe r whole body calcium per kg of soft lean tissue and, probably, L2-L4 B MD. Results of this study also suggest that regular menstrual cycles d o not imply normal ovarian hormone function in young women who are eng aged in either recreational or competitive running.