Lower-Body Strength, Lean Mass, and Bone Mineral Density Across the Adult Lifespan: Age- and Sex-Related Associations

PURPOSE: Aging is associated with declines in muscle strength, lean mass, and bone mineral density (BMD), yet sex-specific lower-body trajectories and their interrelationships across the adult lifespan remain incompletely characterized. The purpose of this study was to determine whether lower-body strength and regional lean mass are differentially associated with hip and lumbar spine BMD across adulthood and whether these relationships vary by age and sex. METHODS: In this cross-sectional study ( n = 251; 149 females, 102 males; 18-85 yr), maximal dynamic strength was assessed using a one-repetition maximum leg press. Dual-energy X-ray absorptiometry quantified lumbar spine and hip BMD, lower-body lean mass, and visceral adipose tissue volume. Hierarchical regression models evaluated the effects of age, sex, and age × sex interactions on BMD, with additional models used to test associations between strength, lean mass, and BMD while controlling for adiposity. RESULTS: Hip BMD was lower with increasing age in both sexes, with higher values in males. Leg-press strength and lower-body lean mass were lower with increasing age but were positively associated with hip BMD (β = 0.32-0.45, p < 0.001) independent of age, sex, and adiposity. The strength-hip BMD association was stronger in younger relative to older adults (interaction P = 0.051). Spine BMD demonstrated a significant age × sex interaction, with age-related declines evident in females but not males. CONCLUSIONS: Maximal lower-body strength is strongly associated with hip BMD across adulthood and may serve as a functional marker of skeletal integrity. These findings highlight the need for caution when interpreting lumbar spine dual-energy X-ray absorptiometry measures in aging males and reinforce the importance of preserving neuromuscular quality for skeletal health across adulthood.