Relationship Between Thigh Muscle Mass And Hip Bone Mineral Content And Size In Prepubertal Children

Abstract

A major factor involved in the development of bone and the accrual and maintenance of mineral mass is the action of muscle during physical activity; however, few studies have examined the relationships between specific muscles and bone in humans. PURPOSE The purpose of this study was to examine the relationships between the mass of the thigh muscles and the bone mineral content (BMC) and bone area of the total proximal femur (TPF) in prepubertal children. METHODS Fourteen prepubertal children (6 boys and 8 girls) 8 to 11 years of age were studied. Sexual maturity was assessed by a physician using the Tanner staging technique. Images were collected along the length of the femur using magnetic resonance imaging (GE 1.5 T; TR = 750, TE = 14, FOV = 16, 1 NEX, 512 × 512 matrix). Skeletal muscles at the level of the middle-third of the femur (mid-thigh) were identified and their mass quantified. BMC (g) and bone area (cm2) of the TPF and its subregions [trochanter, intertrochanter (IT) and femoral neck] were examined using dual-energy X-ray absorptiometry (Delphi W, Hologic Inc.). Relationships between muscle and bone were examined using partial correlations (partial r), with femur length and weight as covariates. RESULTS All children were considered prepubertal (Tanner stage 1 for pubic hair development in boys and girls, penis/testicular development in boys, and breast development in girls). Muscle mass of the entire mid-thigh, quadriceps, hamstrings, thigh adductors and gluteus maximus were not related to BMC or bone area of the TPF or its subregions (P >0.05). However, when specific muscles were examined, semitendinosus mass was related to TPF BMC (partial r = 0.59, P = 0.04), IT BMC (partial r = 0.72, P = 0.01) and IT bone area (partial r = 0.63, P = 0.03). Although not statistically significant (P >0.05), vastus lateralis mass was moderately related to TPF BMC (partial r = 0.52, P = 0.09) and IT BMC (partial r = 0.49, P = 0.10), sartorius mass was related to IT BMC (partial r = 0.53, P = 0.07) and IT bone area (partial r = 0.58, P = 0.05), and gracilis mass was related to TPF bone area (partial r = 0.56, P = 0.06) and IT bone area (partial r = 0.51, P = 0.09). CONCLUSIONS The findings suggest that the thigh muscles most strongly related to the mineral content and size of the TPF in prepubertal children are the semitendinosus, vastus lateralis, gracilis and sartorius. The effect of activities that involve these specific muscles on hip BMC and size requires further investigation. The study was supported by the University of Delaware Research Foundation