Ground-reaction Force Versus Joint-reaction Force Exercise On The Bone Response To Exercise In Older Veterans

Older Veterans may be at greater risk for osteoporotic fracture than non-Veterans and exercise is recommended to improve bone health. Prior research found that ground-reaction force exercise (GRF; jumping, walking) results in greater improvements in areal bone mineral density (aBMD) than joint-reaction force exercise (JRF; weightlifting, rowing), but it is unclear how different types of exercise influence volumetric BMD (vBMD) or estimates of bone strength. PURPOSE: The goal of this pilot study was to determine the magnitude of effect of GRF or JRF exercise on vBMD and bone strength at the hip and lumbar spine. METHODS: Eighteen older Veterans (68.4 ± 4 y; 13 men, 5 women) were randomized to 26 weeks of GRF (N = 8) or JRF (N = 10) exercise. Quantitative computed tomography (QCT) scans of the hip and lumbar spine at baseline and post-intervention were analyzed to determine changes in vBMD and bone strength using finite element analysis (FEA). Within-group changes were evaluated by paired t tests. RESULTS: Results are mean and (95% CI). vBMD non-significantly increased at L2 (GRF: 3.1 mg/cm3 (-4.4, 10.5 mg/cm3); JRF: 1.9 mg/cm3 (-1.9, 5.7 mg/cm3)) and the femoral neck (GRF: 5.6 mg/cm3 (-19.9, 28.2 mg/cm3); JRF: 2.9 mg/cm3, 95% CI: -2.5, 8.2 mg/cm3)) for both groups but was increased at L1 for GRF only (GRF: 2.3 mg/cm3 (-2.2, 6.8 mg/cm3); JRF: -0.3 mg/cm3 (-3.6, 3.0 mg/cm3)). Both groups had increases in estimates of bone strength for the FEA hip stance (GRF: 521.1 N (-317.2, 1359.6 N); JRF: 217 N (27.42, 408.4 N)) and hip fall (GRF: 564.9 N (-497.2, 1627.0 N); JRF: 596.4 N (149.0, 1343.9 N)) models. CONCLUSIONS: Both GRF and JRF exercise training may improve vBMD and estimates of bone strength in older Veterans. This pilot failed to meet recruitment targets (N = 50) and is under-powered for within- and between-group comparisons; results are instead intended to inform future studies. Future research should incorporate additional analyses (e.g., statistical shape modeling) and explore any potential sex differences. VA Eastern Colorado GRECC, UM1 TR004399