THE EFFECT OF EXERCISE TYPE AND MECHANICAL LOAD DISTRIBUTION ON BONE ADAPTATIONS IN ELITE ADOLESCENT FEMALE ATHLETES

Abstract

1080 This study examined the relationship between different types of exercises and the mechanical load distribution patterns of different sports on bone mineral density (BMD-g cm−2) in elite (state or national level) adolescent (15-18y) cyclists (CYC), runners (RUN), swimmers (SWIM), triathletes (TRI) and non-athletic controls (C). Subjects were post-menarcheal with regular menstrual cycles. BMD was assessed by DXA (Lunar DPX Version 3.6 soft-ware) for the total body (TB), lumbar spine (LS-L2-L4), and femoral neck (FN). There were no differences among groups for age, height, weight, age at menarche and body fat percentage. However, SWIM had a significantly (p<0.05) longer sport specific training history (5.5y±1.2y) than CYC (2.6y±0.3y). RUN (1.216±0.04) and TRI (1.182±0.17) had significantly greater areal TBBMD than C (1.102±0.02-mean±SEM). RUN also had significantly higher FNBMD (1.206±0.08) than SWIM 1.001±0.04) and C (1.04±0.03), and CYC (1.318±0.07) had higher (p<0.05) LSBMD than C (1.143±0.05) and SWIM (1.184±0.03). In conclusion, cycling a weight-supported exercise with high muscular force requirements was associated with higher site-specific (LS) BMD than swimming with lower muscular force requirements, and running, a predominately weight-bearing activity was associated with higher BMD than triathalon, a sport combining weight and non-weight bearing exercise, but with a more disperse distribution of mechanical loads.