# Biomechanical Characteristics of Compensatory Reactive Step Responding to the Simulated Trip Perturbation While Walking in Community‐Dwelling People With Stroke: A Cross‐Sectional Study

## TL;DR

This study compares how stroke survivors and healthy people adjust their body movements when recovering from a simulated trip while walking.

## Contribution

The study introduces phase-specific biomechanical adaptations in stroke survivors during reactive stepping after a trip.

## Key findings

- Stroke participants showed increased trunk and knee flexion on the perturbed side compared to controls.
- Phase-specific differences included increased shoulder abduction and altered ankle movement during the reactive step cycle.
- Altered upper limb strategies and reduced ankle dorsiflexion moment were observed in stroke survivors.

## Abstract

Falls pose a significant public health risk for community‐dwelling stroke survivors. Current research on biomechanical parameters to trip perturbation in standing tasks often fails to predict fall risk or balance recovery during dynamic tasks such as walking. Moreover, phase‐specific biomechanical adaptations during recovery from perturbations remain underexplored. One‐dimensional statistical parametric mapping (SPM1D) was used in the current research for analyzing time‐series biomechanical data and to investigate joint angular profiles during reactive stepping following trip‐like gait perturbations. The aim was to compare these biomechanical characteristics between stroke survivors and healthy controls.

Fourteen participants with stroke and ten healthy controls were assessed using a 16‐camera motion capture system. Participants walked at self‐selected usual walking speeds on a split‐belt treadmill and underwent a simulated trip perturbation, triggered by backward treadmill acceleration during initial foot contact. Biomechanical variables at the reactive step touchdown were derived using the Vicon plug‐in‐gait full‐body model. Biomechanical characteristics (joint angles and moments) showing significant between‐group differences at reactive step touchdown were initially identified, and SPM1D was then utilized to analyze joint angles and moments across three equal phases of the reactive step cycle (initial, middle, and end). Independent‐samples t‐tests complemented SPM1D were used to identify between‐group differences, with significance set at p ≤ 0.05.

Compared to controls, stroke participants showed increased trunk flexion, knee flexion, and ankle dorsiflexion angles on the perturbed side, along with decreased ankle dorsiflexion moment and altered upper limb movement strategies. SPM1D revealed phase‐specific differences that increased shoulder abduction during the initial phase on the reactive step side, increased shoulder external rotation in the middle phase on the perturbed side, and greater trunk flexion and ankle dorsiflexion angle but reduced ankle dorsiflexion moment on the perturbed side during the end phase.

Participants with stroke exhibit distinct, phase‐dependent biomechanical adaptations during reactive stepping post‐trip perturbation.