Within-session propulsion asymmetry changes have a limited effect on gait asymmetry post-stroke

 

Right now I have zero propulsion, the whole leg is swung from the hip. And that will never get better until my SPASTICITY IS CURED!

Within-session propulsion asymmetry changes have a limited effect on gait asymmetry post-stroke

• Sarah A. Kettlety,
• James M. Finley &
• Kristan A. Leech 

Journal of NeuroEngineering and Rehabilitation volume 22, Article number: 9 (2025) Cite this article

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Abstract

Background

Biomechanical gait impairments, such as reduced paretic propulsion, are common post-stroke. Studies have used biofeedback to increase paretic propulsion and reduce propulsion asymmetry, but it is unclear if these changes impact overall gait asymmetry. There is an implicit assumption that reducing propulsion asymmetry will improve overall gait symmetry, as paretic propulsion has been related to numerous biomechanical impairments. However, no work has investigated the impact of reducing propulsion asymmetry on overall gait asymmetry. We aimed to understand how within-session changes in propulsion asymmetry affect overall gait asymmetry in individuals post-stroke, operationalized as the combined gait asymmetry metric (CGAM). We hypothesized that decreasing propulsion asymmetry would reduce CGAM. Methods. Participants completed twenty minutes of biofeedback training designed to increase paretic propulsion. We calculated the change in propulsion asymmetry magnitude (Δ|PA|) and the change in CGAM (ΔCGAM) during biofeedback relative to baseline. Then, we fit a robust linear mixed-effects model with ΔCGAM as the outcome and a fixed effect for Δ|PA|. Results. We found a positive association between Δ|PA| and ΔCGAM (β = 2.6, p = 0.002). The average Δ|PA| was -0.09, suggesting that, on average, we would expect a CGAM change of 0.2, which is 0.5% of the average baseline CGAM value. Conclusions. Reducing propulsive asymmetry using biofeedback is unlikely to produce substantial reductions in overall gait asymmetry, suggesting that biofeedback-based approaches to reduce propulsion asymmetry may need to be combined with other interventions to improve overall gait asymmetry. Clinical Trial Registration. NCT04411303.

Background

Individuals post-stroke commonly present with biomechanical gait impairments such as increased spatiotemporal asymmetries, reduced paretic propulsion, and reduced swing knee flexion [1, 2]. Paretic propulsion is a popular target for clinical interventions and research studies because it is associated with walking speed in individuals post-stroke [3,4,5,6] and can be increased using a variety of interventions (gait biofeedback [7], functional electrical stimulation [8, 9], robotics [10], etc.). Additionally, repeated training targeting paretic propulsion can improve functional balance, walking speed [8], and cost of transport [11]. Research studies investigating these interventions mainly focus on quantifying the changes in paretic propulsion or propulsion asymmetry and do not consider whether changes in paretic propulsion impact symmetry in other gait impairments. The assessment of stroke survivor stakeholder values indicates that overall gait asymmetry (i.e., gait appearance) is a priority to address during rehabilitation [12], making it important to understand how an intervention impacts overall gait asymmetry.

There is an implicit assumption that reducing propulsion asymmetry will result in improved symmetry in the entire gait pattern, as paretic propulsion has been related to numerous biomechanical impairments such as paretic knee flexion [13], paretic and non-paretic trailing limb angle [14], and paretic step length [3]. However, no work has directly investigated the impact of reducing propulsion asymmetry on overall gait asymmetry. With numerous degrees of freedom in the lower limb, it is possible that reducing propulsion asymmetry may not reduce other biomechanical impairments and, therefore, may not improve overall gait asymmetry.

The primary aim of this study was to understand how within-session changes in propulsion asymmetry affect overall kinematic and spatiotemporal gait asymmetry in individuals with chronic stroke, operationalized by the combined gait asymmetry metric (CGAM) [15, 16]. This is a first step to understanding what kinematic and spatiotemporal changes might be expected if propulsion asymmetry was reduced in the clinic through biofeedback or other interventions. The CGAM provides a single comprehensive measure of overall kinematic and spatiotemporal gait asymmetry (bounded between 0 and 200), allowing for the inclusion of any biomechanical impairment [15, 16]. With CGAM, we can assess the impact of changing propulsion asymmetry on overall gait asymmetry, not just on a single biomechanical impairment. To manipulate propulsion asymmetry, we used visual biofeedback to increase paretic propulsion. Because of paretic propulsion’s relationship with numerous biomechanical impairments [3, 13, 14], we hypothesized that a decrease in propulsion asymmetry would reduce CGAM.

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