BONE DENSITY AND BODY COMPOSITION RESPONSES TO TRAINING AND DETRAINING IN FEMALE COLLEGIATE VOLLEYBALL PLAYERS

Abstract

Cross-sectional reports show that young adult female volleyball players exhibit higher hip and spine bone mineral density (BMD) compared to their sedentary counterparts. The purpose of this preliminary study was to examine changes in BMD and body composition in response to rigorous volleyball training following a period of reduced sport-specific training. Eight collegiate volleyball players (19–23yrs.; 165–185cm; 62–85kg; 18–26%BF) were measured over two consecutive time periods (3-month off-season followed by 4-month competitive season). Changes in BMD of the hip (femoral neck (FN), greater trochanter (GT), total hip (Thip), lumbar spine (LS) and whole body (WB) and body composition (lean body mass (LBM), fat mass (FM) were assessed by DXA (QDR-4500A). On average, volleyball players possessed BMD values 20–28% higher than age-matched referents, but average body composition compared to age norms. During the off-season, BMD was lost at all hip sites and was maintained at the spine and whole body (% change: FN: −2.1%; GT: −1.4%; Thip: −2.7%; LS: −0.1%; WB: +0.5%), lean mass increased slightly, while fat mass decreased (LBM: +0.7kg; FM: −2.4kg). Following the competitive season, BMD increased at all hip sites but remained unchanged at the spine and whole body (% change: FN: +1.6%; GT: +1.8%; Thip: +3.3%; LS: −0.1%; WB: +0.7%), lean mass decreased slightly, while fat mass increased (LBM: −0.5kg; FM: +1.0kg). Percent changes between the off- and competitive seasons were significantly different for FN BMD (p = 0.03) and FM (p = 0.01) and nearly so for GT BMD (p = 0.08). There were no significant correlations between BMD and body composition changes. We conclude that hip BMD and fat mass decrease when sport-specific training ceases, but are regained when training resumes.