Center Of Mass Trajectory In Lower Extremity During Simulated Ankle Sprain

In accordance with the inverted pendulum model, center of mass (CoM) trajectories provide an indication of postural stability during gait. However, there is little research quantifying the CoM trajectory following perturbation of the ankle during gait. An understanding of CoM positioning in response to sudden dynamic ankle perturbation could be beneficial to elucidating ankle injury avoidance strategies. PURPOSE: Compare post heel strike CoM trajectories across perturbed and normal gait conditions. METHODS: Eleven healthy volunteers walked along a walkway embedded with two trapdoors that elicit sudden inversion, or inversion and plantarflexion. Participants performed trials of walking gait during normal (NW), inversion (INV), and inversion/plantarflexion perturbation (PF) conditions. Lower extremity trajectories were collected and used to estimate the lower extremity model CoM location. Mediolateral and anteroposterior displacement and total path were calculated within a 200 ms post heel strike window. Repeated measures ANOVAs were employed to assess differences in COM trajectory across conditions. RESULTS: No significances were observed for center of mass trajectory for both total displacement [INV (0.0186 ± 0.0035 m), PF (0.015 ± 0.005 m), NW (0.017 ± 0.0058 m)] or total mediolateral distance [INV (0.0188 ± 0.003 m), PF (0.0175 ± 0.006 m), NW (0.0175 ± 0.005 m)], as well as total displacement [INV (0.187 ± 0.02 m), PF (0.165 ± 0.049 m), NW(0.187 ± 0.018 m)] or anteroposterior total distance [INV (0.187 ± 0.023 m), PF (0.194 m ± 0.056 m), NW (0.19 ± 0.018 m)]. CONCLUSIONS: Significant differences in CoM trajectories were not observed across conditions, which may indicate a sufficient neuromuscular response during perturbation trials to normalize CoM trajectories. Alternatively, the perturbations may not have been strong enough to invoke differences in CoM trajectory across conditions. Future studies should explore measures of neuromuscular control that could explain CoM behavior in response to sudden ankle perturbations.