D-35 Free Communication/Poster - The Aging Cardiovascular System and Exercise

Abstract

Bone mass at the proximal femur (PF) may be influenced by both physical activity (PA) and bone geometry. Since bone geometry also appears to be determined by PA it is reasonable to analyze the relationship between these variables and determine the contribution of PA and geometry in bone mass. PURPOSE:To examine associations of PA with geometric characteristics of the pelvis-PF structure and with bone mineral density (BMD) of fracture-critical bone regions of PF. METHODS:Participants were 85 young adults, 50 females (age: 23.7±3.4 yrs) and 35 males (age: 24.4 ± 3.4 yrs). BMD was measured at the integral, superolateral (SL), and inferomedial (IM) femoral neck (FN), and at the trochanter (TR). These regions were used to represent bone mass distribution via three BMD ratios - FN:PF, IM:SL, and TR:PF. PA was evaluated with accelerometers and with a bone-specific PA questionnaire (BPAQ). Upper inter acetabular distance (UIAD), femoral neck axis length (FNAL), narrow neck width (NNW), abductor lever arm (ALA), and neck-shaft angle (NSA) were used as geometric measures and were derived from a whole body and PF DXA scans. All analyses were adjusted for age, body height, lean mass, calcium intake, and sex. RESULTS:Correlation analyses revealed that PA is positively associated with FNAL and NNW and negatively associated with UIAD while sedentary time is positively associated with UIAD (p<0.05). It were also observed positive associations (p<0.05) or a trend for positive associations (p=0.056 - 0.078) between PA and BMD at all bone regions. UIAD associated with TR BMD (r=-0.328, p=0.006) and ALA with FN:PF (r=-264,p=0.027). Stepwise regression models showed that PA (BPAQ or vigorous PA) explains up to 9% of the variance of the TR, integral, IM, and SL FN BMD (p<0.05) but with higher explanation at the TR than at FN regions. There was a negative association between UIAD and TR BMD (R2=4%, p=0.002), and between ALA and FN:PF (R2=9%, p=0.004). It was found a negative association between NSA and TR BMD (R2=6%, p=0.035) only in females. CONCLUSIONS:Despite being interrelated, PA and geometric characteristics of the pelvis-PF structure are independently associated to bone mass at PF regions. This work was funded by Portuguese Science and Technology Foundation (PTDC/DES/115607/2009) and PhD Scholarship (SFRH/BD/79828/2011).