AbstractMediolateral dynamic stability control is challenging for older-adults (OA) and is associated with lateral falls and hip fracture. Previous research examining the eccentricity of the net ground reaction force (GRFnet) and individual-limb GRFs have helped elucidate why OA exhibit greater mediolateral instability during stepping responses. The present work sought to understand the individual-limb contributions to mediolateral stability during gait, by examining whole-body kinematics and eccentricity of individual-limb GRFs. 28 younger-adults (YA) (18-31 years) and 28 OA (>65 years) completed 10 walking trials at a self-selected speed and step placement, all were right-limb dominant. Whole-body COM kinematics and individual-limb GRFs were quantified. The minimum distance between the COM and the lateral aspect of the BOS during each step was quantified (dmin) as a measure of kinematic instability. The eccentricity of individual-limb GRFs relative to the COM were calculated (?d) throughout the stance-phase. Positive and negative eccentricities of the individual-limb GRF were quantified using the mean difference (MD). Positive values are believed to be restabilizing (MDpos), limiting lateral COM displacement; negative values are destabilizing (MDneg). OA exhibited significantly greater dominant-side dmin and MDneg than YA. Larger dominant-side dmin among OA may suggest this is a strategy to maintain a larger margin of stability. The lack of no age-related differences on the non-dominant side may indicate OA inappropriately scale, which could increase the risk of lateral falls towards this side. Larger dominant-side MDneg could be restabilizing if caused by a larger medially directed GRF component, limiting the lateral linear acceleration of the COM.
Acknowledgments: Support for this research was provided by the Manitoba Medical Service Foundation and the Natural Sciences and Engineering Research Council of Canada (NSERC).