Biomechanics of a Drop Landing: Osteogenic Stimulus Measures May Vary.

Objectives: Impact exercises are known to increase bone mineral density (BMD) through the biological process of bone remodeling, increasing strength and resistance to fracture. The purpose of this study was to compare several measures that have been used as surrogates for bone impact as a magnitude of its potential to induce bone remodeling.

Methods: Twenty healthy adults (10 male, 10 female) participated in a biomechanical investigation of how drop height and landing style (bilateral vs. unilateral) affect various estimates of bone remodeling stimuli. These stimuli surrogates include accelerations measured by Inertial Measurement Units (IMUs), ground reaction forces, joint contact forces estimated by musculoskeletal modeling, and tibia strains estimated by finite element modeling.

Results: Drop height was directly related to stimulus magnitudes, but there was little benefit to drop heights greater than 0.4 m. In contrast, switching from a bilateral to a unilateral landing had a large positive effect. A post-hoc analysis revealed that a linear regression of kinematics and reaction force explained up to 79% of the variance in computationally expensive bone remodeling stimulus measures.

Conclusions: subject-specific bone strain analysis may not be necessary to understand the magnitude of a bone remodeling stimulus of an exercise.