Identifying candidates for targeted gait rehabilitation after stroke: better prediction through biomechanics-informed characterization

Abstract

BackgroundWalking speed has been used to predict the efficacy of gait training; however, poststroke motor impairments are heterogeneous and different biomechanical strategies may underlie the same walking speed. Identifying which individuals will respond best to a particular gait rehabilitation program using walking speed alone may thus be limited. The objective of this study was to determine if, beyond walking speed, participants’ baseline ability to generate propulsive force from their paretic limbs (paretic propulsion) influences the improvements in walking speed resulting from a paretic propulsion-targeting gait intervention.MethodsTwenty seven participants >6 months poststroke underwent a 12-week locomotor training program designed to target deficits in paretic propulsion through the combination of fast walking with functional electrical stimulation to the paretic ankle musculature (FastFES). The relationship between participants’ baseline usual walking speed (UWSbaseline), maximum walking speed (MWSbaseline), and paretic propulsion (propbaseline) versus improvements in usual walking speed (∆UWS) and maximum walking speed (∆MWS) were evaluated in moderated regression models.ResultsUWSbaseline and MWSbaseline were, respectively, poor predictors of ΔUWS (R2 = 0.24) and ΔMWS (R2 = 0.01). Paretic propulsion × walking speed interactions (UWSbaseline × propbaseline and MWSbaseline × propbaseline) were observed in each regression model (R2s = 0.61 and 0.49 for ∆UWS and ∆MWS, respectively), revealing that slower individuals with higher utilization of the paretic limb for forward propulsion responded best to FastFES training and were the most likely to achieve clinically important differences.ConclusionsCharacterizing participants based on both their walking speed and ability to generate paretic propulsion is a markedly better approach to predicting walking recovery following targeted gait rehabilitation than using walking speed alone.

Paretic propulsion as a measure of walking performance and functional motor recovery post-stroke: A review

“…While the interventions described here can lead to increased paretic limb output, not all persons with hemiparesis improve Pp with therapy [23,24] and even in those who do increase Pp, propulsion deficits on the paretic limb can persist [53]. Moreover, the individuals with the most severe propulsion asymmetries have been shown to benefit least from current rehabilitation techniques [53,58], which suggests there exists a baseline threshold of plantarflexor function to benefit from current locomotor rehabilitation techniques [18]. However, such a threshold has not been defined and likely depends on the type of locomotor rehabilitation being utilized.…”

“…A follow-up study with a larger group of hemiparetic subjects determined that slower hemiparetic walkers with greater Pp at baseline achieved the greatest improvements in self-selected and fastest walking speeds with Fast-FES training compared to walkers with smaller Pp and even faster walkers with high Pp [18]. Furthermore, their findings demonstrated that baseline Pp was important for predicting changes in self-selected and fastest walking speed due to training and suggested that walking speed alone was insufficient for identifying candidates for targeted gait training because, as shown above, walking speed alone does not distinguish between underlying hemiparetic motor impairments [18].…”

“…However, such a threshold has not been defined and likely depends on the type of locomotor rehabilitation being utilized. In addition, it is unclear if individuals with sub-threshold plantarflexor function at baseline are incapable of improving paretic plantarflexor function due to impaired corticomotor function [68] or if reliance on a compensation strategy that hinders propulsion is interfering with their ability to learn a propulsion-based walking strategy [18]. Future work is needed to determine how to identify the cause of subthreshold plantarflexor function at the onset of therapy as well as to develop interventions specific to the underlying cause that are capable of improving Pp.…”

“…Pp has been shown to strongly correlate with hemiparetic severity (based on the Brunnstrom motor recovery stages [12], Figure 1) [6], suggesting improvements in propulsion symmetry may lead to improved motor function in the paretic limb. Consequently, Pp has emerged as a common mechanics-based measure of hemiparetic walking performance [13][14][15][16] and recently therapies have targeted propulsion as a primary outcome [17] and predictor of gait outcomes [18].…”

Self-perceived functioning and disability after randomized conventional and electromechanically-assisted gait training in subacute stroke: A 6 months follow-up

“…In normal gait, the role of the ankle plantar flexors is however essential in contributing to forward propulsion [28,169]. Paretic propulsion, defined as the contribution of the paretic leg in driving the body forward during walking, has recently been suggested as an important measure of walking performance post stroke [169,170]. Less paretic propulsion has also been associated with more severe hemiparesis, and with less leg extension with the paretic limb during terminal stance [169], again highlighting the importance of hip extensor strength during gait post stroke.…”