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

INTRODUCTION/

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 (1RM) 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 DXA measures in aging males and reinforce the importance of preserving neuromuscular quality for skeletal health across adulthood.