Independent and synergistic effects of visual biofeedback and phase-specific belt deceleration on affected-leg propulsion in post-stroke split-belt treadmill training

Background. Post-stroke walking deficits are closely associated with impaired forward propulsion from the affected leg. We developed a real-time training system using an instrumented split-belt treadmill that provides phase-specific adaptive belt speed modulation (propulsion-facilitating mode, PF) during late stance and visual biofeedback (VB) of the affected leg’s propulsive (anterior ground reaction) force. This study investigated the effects of VB, PF, and VB + PF on gait propulsion, kinematics, and muscle activity in individuals post-stroke. Methods. Thirteen adults with chronic hemiparetic stroke completed three randomized, counterbalanced treadmill trials: VB alone, PF alone, and VB + PF. Each trial consisted of the baseline (30 steps, without intervention), the training (100 steps, assigned modality), and the post-training (30 steps, without intervention) periods. All outcome measures were obtained from the affected leg, including peak propulsive force, stride length, peak knee and ankle extension, and electromyographic activity of the major ankle and knee extensors (i.e., medial gastrocnemius, soleus, vastus medialis, and rectus femoris). Results. Significant main effects of modality, period, and their interaction were observed for all outcome measures (P < 0.0001). During the training period, VB + PF resulted in the greatest improvements across all outcome measures (i.e., peak propulsive force, stride length, peak knee and ankle extension, and electromyographic activity in the ankle and knee extensor muscles) compared with either VB or PF alone. PF alone demonstrated moderate improvements, whereas VB alone showed smaller yet statistically significant improvements. Regardless of modality, the improvements achieved during the training period were retained during the post-training period. Conclusion. In individuals post-stroke, combining real-time visual biofeedback with phase-specific adaptive belt speed modulation resulted in the greatest and most substantial improvements in affected-leg propulsion, lower-limb kinematics, and electromyographic activity in the ankle and knee extensor muscles. These findings demonstrate the effectiveness of multimodal, adaptive treadmill training in engaging the affected-leg propulsion reserve and inform the development of scalable rehabilitation protocols that integrate perceptual feedback with task-specific mechanical facilitation for stroke gait rehabilitation.