EFFECTS OF INTRINSIC AND EXTRINSIC FEEDBACK ON PARETIC LIMB CONTRIBUTION IN PROPULSION GENERATION DURING SPLIT-BELT TREADMILL WALKING IN CHRONIC POST-STROKE INDIVIDUALS

Abstract

Stroke is a leading cause of long-term disability and results in locomotor impairments that limit independence and community participation. One of the most common consequences of stroke is hemiparesis, which contributes to gait asymmetry characterized by reduced contribution of the paretic limb during walking. Propulsion asymmetry, in particular, has been associated with slower walking speed, increased energetic cost, reduced functional mobility, and diminished quality of life. Thus, improving paretic propulsion has become an important target of post-stroke gait rehabilitation. The overarching goal of this dissertation was to advance the understanding of how intrinsic feedback, extrinsic feedback, combined feedback, and propulsion-demand manipulations influence the biomechanical and locomotor mechanisms underlying propulsion generation and to inform the development of targeted rehabilitation interventions that enhance paretic limb contribution during walking. This dissertation consisted of three studies. Study 1 examined whether intrinsic feedback delivered through backward resistive force (BRF) and extrinsic feedback delivered through visual feedback generate equivalent propulsion outputs during split-belt treadmill walking in healthy adults. Study 2 investigated the immediate effects of intrinsic, extrinsic, and combined feedback on paretic propulsion contribution during split-belt treadmill walking in individuals post-stroke. Study 3 examined the effects of increasing BRF during tied- and split-belt treadmill walking on lower-extremity mechanical work in individuals post-stroke and age-similar unimpaired adults. The findings showed that propulsion can be modified through multiple feedback modalities and propulsion-demand manipulations. Healthy adults achieved similar propulsion targets using intrinsic and extrinsic feedback but relied on distinct biomechanical strategies. In individuals post-stroke, combined feedback produced greater improvements in paretic propulsion contribution than either feedback modality alone, and these improvements were associated with increases in trailing limb angle and stance time. Increasing propulsion demands through BRF resulted in proportional increases in lower-extremity mechanical work in unimpaired adults, whereas individuals post-stroke exhibited limb- and configuration-specific responses, with the paretic limb showing a limited ability to scale mechanical output under certain walking conditions. Collectively, the findings provide new insight into the biomechanical mechanisms underlying propulsion generation and support the development of individualized propulsion-focused rehabilitation interventions that integrate feedback strategies and locomotor task demands to reduce propulsion asymmetry after stroke.