Abstract
Background Regional lean mass, bone mineral content (BMC), and strength are related in young men, but it is less clear how much these relationships simply reflect shared body and skeletal size in resistance-trained individuals. We therefore examined broad regional associations between lean mass and bone measures, together with selected bone and function relationships, with particular attention to body size.Methods This cross-sectional secondary analysis used baseline data from 44 resistance-trained males from a previous four group trial. Whole body dual energy X ray absorptiometry (DXA) provided broad upper body and lower body lean mass measures, BMC, projected bone area, and areal bone mineral density (BMD). We examined associations using Pearson correlations and linear regression with HC3 robust standard errors. Models adjusted for age and height were considered alongside body mass, projected area, and allometric models. Benjamini Hochberg correction across all 18 adjusted cross-sectional tests was prioritized.Results Regional lean mass was positively associated with several BMC outcomes in models adjusted for age and height, including arm BMC (standardized β = 0.605), rib BMC (β = 0.608), leg BMC (β = 0.429), and pelvis BMC (β = 0.550). Several estimates became smaller or less precise when body mass, projected bone area, or allometric scaling was considered. Pelvis BMC was conditionally associated with estimated leg press 1-RM after adjustment for age, height, and lower body lean mass (β = 0.501; 18 test BH q = 0.001). This association, however, cannot distinguish the influence of skeletal size, body proportions, training history, or other unmeasured factors.Conclusions In resistance-trained males, regional DXA lean mass and bone measures appear to form a phenotype that is strongly influenced by body size. Associations from models adjusted for age and height should therefore be interpreted alongside the size conditioned analyzes. The association between pelvis BMC and estimated leg press 1-RM is best viewed as an exploratory conditional finding within this broader phenotype, rather than evidence of a distinct skeletal contribution to strength.