Rc. Klesges et al., CHANGES IN BONE-MINERAL CONTENT IN MALE-ATHLETES - MECHANISMS OF ACTION AND INTERVENTION EFFECTS, JAMA, the journal of the American Medical Association, 276(3), 1996, pp. 226-230
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.