Fastest may not be the best: differential and individual-specific immediate effects of gait speed on biomechanical variables post-stroke

During gait rehabilitation, determining the walking speed that optimizes an individuals biomechanical gait quality is challenging because discrete biomechanical variables used to quantify gait quality change differentially with speed. We recently developed gait signatures that may provide a holistic representation of biomechanical gait quality by implicitly modeling the neuromechanical dynamics of walking. Here, we characterized speed-induced changes in post-stroke gait signatures and their relationship to 14 discrete biomechanical variables in 19 stroke survivors and 5 able-bodied adults walking at 6 speeds. With increasing speed, post-stroke gait signatures became more like able-bodied gait signatures, suggesting improved gait quality. Inter-individual differences in the direction that post-stroke gait signatures changed with speed relative to able-bodied signatures were correlated with walking function (e.g., walking speed; r2=0.53) and discrete biomechanical variables (e.g., paretic-leg propulsion; r2=0.57). These findings suggest that how post-stroke gait signatures change with speed relative to able-bodied signatures reflects neuromechanical constraints that also impact biomechanical gait quality. Across speeds, gait signatures captured holistic biomechanical gait quality, balancing tradeoffs between improved paretic-leg biomechanics and worsened inter-limb asymmetry and gait compensations (r2=0.77). Gait signatures may, therefore, be useful in holistic assessment of inter-and intra-individual differences in biomechanical gait quality, potentially informing rehabilitation personalization.