Supplementary_MaterialR1CleanVersion – Supplemental material for Direction-Specific Instability Poststroke Is Associated With Deficient Motor Modules for Balance Control

<p>Supplemental material, Supplementary_MaterialR1CleanVersion for Direction-Specific Instability Poststroke Is Associated With Deficient Motor Modules for Balance Control by Digna de Kam, Alexander C. Geurts, Vivian Weerdesteyn, and Gelsy Torres-Oviedo in Neurorehabilitation and Neural Repair</p

Raw EMG traces of a representative trial during ankle dorsiflexion.

<p>Gray lines are trials without a SAS, black lines are trials with a SAS. Determined latencies are presented by a dot.</p

Descriptive information on stepping performance.

<p>Top panel: Proportion of participants that were still in the experiment at increasing perturbation intensities. The survival curve shows that the experiment was terminated at lower perturbation intensities in the people with stroke compared to the control subjects (chi² = 4.6, p = 0.032), indicating that their balance recovery capacity was poorer. Lower panels: Descriptive data of spatiotemporal and body configuration parameters for each participant group at the four different perturbation intensities.</p

Body configuration at first stepping-foot contact predicts backward balance recovery capacity in people with chronic stroke

<div><p>Objective</p><p>To determine the predictive value of leg and trunk inclination angles at stepping-foot contact for the capacity to recover from a backward balance perturbation with a single step in people after stroke.</p><p>Methods</p><p>Twenty-four chronic stroke survivors and 21 healthy controls were included in a cross-sectional study. We studied reactive stepping responses by subjecting participants to multidirectional stance perturbations at different intensities on a translating platform. In this paper we focus on backward perturbations. Participants were instructed to recover from the perturbations with maximally one step. A trial was classified as ‘success’ if balance was restored according to this instruction. We recorded full-body kinematics and computed: 1) body configuration parameters at first stepping-foot contact (leg and trunk inclination angles) and 2) spatiotemporal step parameters (step onset, step length, step duration and step velocity). We identified predictors of balance recovery capacity using a stepwise logistic regression. Perturbation intensity was also included as a predictor.</p><p>Results</p><p>The model with spatiotemporal parameters (perturbation intensity, step length and step duration) could correctly classify 85% of the trials as success or fail (Nagelkerke R² = 0.61). In the body configuration model (Nagelkerke R² = 0.71), perturbation intensity and leg and trunk angles correctly classified the outcome of 86% of the recovery attempts. The goodness of fit was significantly higher for the body configuration model compared to the model with spatiotemporal variables (p<0.01). Participant group and stepping leg (paretic or non-paretic) did not significantly improve the explained variance of the final body configuration model.</p><p>Conclusions</p><p>Body configuration at stepping-foot contact is a valid and clinically feasible indicator of backward fall risk in stroke survivors, given its potential to be derived from a single sagittal screenshot.</p></div

Results of the stepwise regression analyses.

<p>Results of the stepwise regression analyses.</p

Participant’s characteristics.

<p>Participant’s characteristics.</p

Predictive value of leg and trunk angles.

<p>Leg and trunk inclination angles for failed and successful recovery attempts at the different perturbation intensities. Solid lines represent the values corresponding to a 50% probability of success as determined by the logistic regression analysis.</p

Descriptive statistics for failed and successful attempts.

<p>Descriptive statistics for failed and successful attempts.</p

Experimental setup for gait measurements.

<p>Left: position of the Vicon markers in frontal plane, Middle: position of the Vicon markers in sagittal plane; Right: skeletal structure generated by the Vicon system (frontal plane view).</p

Kinematic and kinetic symmetry values of the patients.

<p>Kinematic and kinetic symmetry values of the patients.</p