Changes in bone mineral content in male athletes. Mechanisms of action and intervention effects
R. C. Klesges, K. D. Ward, M. L. Shelton, W. B. Applegate, E. D. Cantler, G. M. Palmieri, K. Harmon and J. Davis
Department of psychology, University of Memphis, TN 38152, USA. bklesges@msuvx1.memphis.edu
OBJECTIVES: To determine changes in bone mineral content (BMC) in male
athletes, to examine the mechanisms of changes, and to evaluate the effects
of intervention. DESIGN: Dual-energy x-ray absorptiometry (DEXA) tests were
administered over a 2-year period, and calcium loss during training was
determined by analysis of sweat and urine. Calcium supplementation was
administered during year 2. SETTING--A midsouth university. PARTICIPANTS:
Eleven members of a college Division I-A basketball team. INTERVENTION:
Based on observed calcium loss, athletes received differential levels of
calcium supplementation. Intervention commenced the week prior to the fall
training season and continued through postseason play. MAIN OUTCOME
MEASURE--Changes in BMC. RESULTS: Total body BMC decreased 3.8% from
preseason to midseason of year 1 (mean decrease, 133.4 g, P = .02),
increased nonsignificantly by 1.1% (mean increase, 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 247 mg [corrected] per training session. From 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 supplementation was associated with
significant increases in BMC and lean body mass. CONCLUSIONS: Bone loss is
calcium related and exercise is positively related to BMC provided that
calcium intake is sufficient to offset dermal loss.
