Association of body composition and muscle function with hip geometry and BMD in premenopausal women

Background: Muscle mass and function are related to bone mineral density (BMD) but associations with bone geometry and BMD at differently loaded hip regions are less well-known. Aim: To examine associations of muscle strength, maximal impact forces and body composition with hip bone density and geometry. Subjects and methods: In 88 sedentary, premenopausal women (32.6 +/- 8.5 years), fat-free mass (FFM), isometric knee extension strength (IKES), and peak landing ground reaction force (GRF) were measured. BMD at the proximal femur and sub-regions, section modulus (Z), and cross-sectional area (CSA) were estimated using dual X-ray absorptiometry. Results: BMD at hip sites was significantly associated with body mass, IKES, GRF and FFM (r = 0.31-0.50) whilst Z and CSA were correlated with FFM (r = 0.67 and 0.62, respectively). In multivariate models, variables explaining most variance were body mass for lower neck and shaft BMD (25% and 17%, respectively), IKES for upper neck BMD (21%), GRF for trochanter (19%) and total hip BMD (18%) and FFM for femoral neck Z, CSA and BMD (54%, 38% and 20%, respectively). Conclusion: BMD at superolateral hip sites was most strongly related to muscle function and maximal impact forces, BMD at inferiomedial hip sites to body mass, and hip geometry to FFM.