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Mechanisms of Action and Intervention Effects

Robert C. Klesges, PhD; Kenneth D. Ward, MS; Mary L. Shelton, PhD; William B. Applegate, MD, MPH; Edwin D. Cantler, MEd; Genaro M. A. Palmieri, MD; Karen Harmon; James Davis, PharmD

JAMA. 1996;276(3):226-230.

Abstract
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 l-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 (meandecrease, 133.4g, P=.02), increasednonsignificantlyby 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 422 mg 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.

Author Affiliations
From the Universities Prevention Center, Department of Psychology (Drs Klesges and Shelton, Mr Ward, and Ms Harmon), and Department of Athletics (Mr Cantler), University of Memphis (Tenn); and Departments of Preventive Medicine (Dr Applegate), Medicine (Dr Palmieri), and the University Pharmacy (Dr Davis), the University of Tennessee, Memphis.

Footnotes
A patent application has been submitted for the calcium supplement drink used in this study. The University of Memphis holds the intellectual property rights if a patent is awarded. However, it is the policy of the university to transfer 30% of the net proceeds from the licensing of intellectual property to the inventors (R.C.K., E.D.C.) of the intellectual property.

Reprints: Robert C. Klesges, PhD, Universities Prevention Center, Department of Psychology, University of Memphis, Memphis, TN 38152 (e-mail: bklesges@ msuvx1.memphis.edu).

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