Lean Mass Is More Strongly Associated With Bone Microarchitecture Than Fat Mass In Army Trainees

Musculoskeletal injuries (MSKIs), such as stress fractures, are a leading cause of attrition in US Army trainees during Basic Combat Training (BCT). Improvements in body composition, bone density, and microarchitecture have been shown to decrease MSKI risk. Attempts to mitigate MSKI risk in trainees primarily target reduction in fat mass, but the independent relationships of fat and lean masses with bone parameters have yet to be defined. PURPOSE: To determine the independent effects of fat and lean mass on bone density and microarchitecture in BCT trainees. METHODS: Whole body dual-energy X-ray absorptiometry (DXA) scans were completed in 2,225 trainees (1,400 M, 825 F) to assess fat and lean mass. High-resolution peripheral quantitative computed tomography (HRpQCT) was used to evaluate total volumetric bone mineral density (Tt.BMD), trabecular volumetric BMD (Tb.BMD), the ratio of trabecular bone volume to total bone volume (Tb.BV/TV), and trabecular thickness (Tb.Th) at the distal tibia. Partial correlations were conducted to assess individual relationships between lean and fat mass with bone parameters while adjusting for sex, age, and height. RESULTS: Subject characteristics were as follows (mean ± SD): age: 21 ± 4 yrs; body mass: 71.8 ± 12.4 kg; height: 171 ± 10 cm; fat mass: 20.0 ± 5.0 kg; lean mass, 41.1 ± 5.5 kg. Partial correlations indicate that lean mass is more highly correlated to bone parameters than fat mass (Table). CONCLUSION: Lean mass is more strongly associated with bone density and microarchitecture than fat mass in US Army BCT trainees. Training programs designed to mitigate MSKI risk through optimizing bone health should prioritize development of lean mass rather than reduction in fat mass. - Tt.BMD Tb.BMD Tb.BV/TV Tb.Th Fat Mass (kg) 0.092* 0.110* 0.114* -0.018 Lean Mass (kg) 0.357* 0.356* 0.357* 0.260* *p < 0.001Disclaimer: The opinions or assertions contained herein are the private views of the author(s) and are not to be construed as official or as reflecting the views of the Army, the Department of Defense, or the U.S. Government.