CHANGES IN BONE-MINERAL CONTENT IN MALE-ATHLETES - MECHANISMS OF ACTION AND INTERVENTION EFFECTS

Objectives.-To determine changes in bane mineral content (BMC) in male athletes, to examine the mechanisms of changes, and to evaluate the e ffects of intervention. Design.-Dual-energy x-ray absorptiometry (DEXA ) tests were administered over a 2-year period, and calcium loss durin g training was determined by analysis of sweat and urine. Calcium supp lementation was administered during year 2. Setting.-A midsouth univer sity. Participants.-Eleven members of a college Division I-A basketbal l team. Intervention.-Based on observed calcium loss, athletes receive d differential levels of calcium supplementation. intervention commenc ed the week prior to the fall training season and continued through po stseason play. Main Outcome Measure.-Changes in BMC. Results.-Total bo dy BMC decreased 3.8% from preseason to midseason of year 1 (mean decr ease, 133.4 g, P=.02), increased nonsignificantly by 1.1% (mean increa se, 35.3 g, P=.22) during the offseason, but decreased an additional 3 .3% during summer months when practices resumed (mean decrease, 113.1 g, P=.01). Dermal calcium loss averaged 422 mg per training session, F rom preseason to late summer, there was an overall decrease of 6.1% in total BMC and a 10.5% decrease in BMC of the legs, Calcium supplement ation was associated with significant increases in BMC and lean body m ass. Conclusions.-Bone loss is calcium related and exercise is positiv ely related to BMC provided that calcium intake is sufficient to offse t dermal loss.