Ground Compliance Improves Retention of Visual Feedback-Based Propulsion Training for Gait Rehabilitation

TL;DR

This study addresses propulsion deficits in gait rehabilitation by testing whether coupling unilateral ground compliance with real-time visual feedback of vertical ground reaction forces yields larger and more durable push-off force (POF) gains than visual feedback alone. Using the Variable Stiffness Treadmill 2, with a low-stiffness left belt during training and real-time POF targets, the authors show sustained POF increases and lasting changes in muscle activity and joint angles, especially when compliant terrain is present. The results imply that visual and proprioceptive integration on a compliant surface enables more natural propulsion strategies and bilateral coordination, with potential to improve gait symmetry after stroke. The work provides a foundation for incorporating compliant terrain into robot-assisted gait rehabilitation to enhance propulsion outcomes.

Abstract

This study investigates whether adding ground compliance to visual feedback (VF) gait training is more effective at increasing push-off force (POF) compared to using VF alone, with implications for gait rehabilitation. Ten healthy participants walked on a custom split-belt treadmill. All participants received real-time visual feedback of their ground reaction forces. One group also experienced changes in ground compliance, while a control group received only visual feedback. Intentional increases in propulsive ground reaction forces (POF) were successfully achieved and sustained post-intervention, especially in the group that experienced ground compliance. This group also demonstrated lasting after-effects in muscle activity and joint kinematics, indicating a more robust learning of natural strategies to increase propulsion. This work demonstrates how visual and proprioceptive systems coordinate during gait adaptation. It uniquely shows that combining ground compliance with visual feedback enhances the learning of propulsive forces, supporting the potential use of compliant terrain in long-term rehabilitation targeting propulsion deficits, such as those following a stroke.

Figures (7)

• Figure 1: Experimental setup showing a representative participant wearing reflective markers and EMG electrodes on the legs while walking on VST 2 equipped with the force sensing mats, and observing the visual feedback monitor.
• Figure 2: Close look of the visual feedback shown to the participants with training feedback shown on top and trial feedback shown on the bottom. The axes units, labels, or legends are not shown to the participants, but are included in the figure for clarity, with Baseline (BL) values given with respect to (wrt) percent bodyweight (BW).
• Figure 3: For each group, the visual feedback used is shown on the left, with the relative number of gait cycles in each trial half proportioned through time, and for each belt individually. Each group received the same visual feedback and was equally trained to increase POF.
• Figure 4: Peak vertical POF values for all participants in each group, normalized to the average POF during the last baseline (BL) phase for each participant individually. Colored bars indicate a significant increase between each half of the observation phase and the entire baseline phase.
• Figure 5: GRF profile for both legs during the final trial half for a representative participant from each group. All force values are normalized with respect to body weight (BW) in order to accurately show comparisons. Blue corresponds to the low stiffness group, while orange denotes the rigid group. For each group, the darker color represents the observation (OB) phase, with the baseline (BL) phase given by the lighter color .