Impaired pendulum-like mechanics during post-stroke walking: a biomechanical comparison with healthy individuals

Introduction After stroke, many individuals recover the ability to walk independently. However, post-stroke gait remains inefficient and energetically demanding. Alterations in the pendulum-like exchange of mechanical energy of the center of mass (CoM) may contribute to gait inefficiency. Methods 30 post-stroke individuals and 30 healthy controls walked at self-selected speed while 3D motion capture data were collected with an optoelectronic system. Spatio-temporal gait parameters were computed, and CoM mechanical energy was estimated from pelvic marker trajectories. Mechanical efficiency was quantified using the Energy Recovery Index (ERI) and Congruity (C) between potential and kinetic energy. Between-group differences were assessed using independent-samples t -tests, and analyses accounting for walking speed were performed for mechanical outcomes. Within the stroke group, correlations were computed between ERI and selected spatio-temporal and functional parameters, including the Locomotor Rehabilitation Index (LRI). Results Compared with healthy controls, post-stroke participants exhibited significantly reduced walking speed, shorter step and stride lengths, and prolonged double support time ( p < 0.05). Mechanical energy recovery was significantly lower in the stroke group (ERI: 54.4 ± 12.7%) than in healthy participants (68.1 ± 4.6%), while C was significantly higher ( p < 0.05), indicating altered pendulum-like mechanics. Differences in ERI and congruity could not be explained by walking speed alone. In the stroke group, ERI was positively correlated with step length and LRI, and negatively correlated with double support time and non-plegic limb foot-off timing ( p < 0.01). Discussion Post-stroke walking is characterized by impaired pendulum-like mechanics of the CoM that are not solely attributable to reduced walking speed. Mechanical energy recovery is closely associated with spatio-temporal and functional gait characteristics, supporting the use of biomechanical indices such as ERI to complement conventional gait assessment and plan targeted rehabilitation strategies.