A novel system for introducing precisely-controlled, unanticipated gait perturbations for the study of stumble recovery

You should be able to recover as easily as this robot dog does from being kicked. What is your doctor and therapist doing to ensure you can recover from perturbations? Mine did nothing, all my ability to recover was my prior life whitewater canoeing and cross-country skiing. I could kneel on a yoga ball and stay upright.  

Boston Dynamics have released a video of 'Spot' - a four-legged robot that can run, walk and sustain a kicking.

Th latest here:

A novel system for introducing precisely-controlled, unanticipated gait perturbations for the study of stumble recovery

• Shane T. King†,
• Maura E. Eveld†Email author,
• Andrés Martínez,
• Karl E. Zelik and
• Michael Goldfarb

†Contributed equally

Journal of NeuroEngineering and Rehabilitation201916:69

https://doi.org/10.1186/s12984-019-0527-7

©  The Author(s) 2019

• Received: 20 December 2018
• Accepted: 30 April 2019
• Published: 10 June 2019

Abstract

Background

The experimental study of stumble recovery is essential to better understanding the reflexive mechanisms that help prevent falls as well as the deficiencies in fall-prone populations. This study would benefit from a system that can introduce perturbations that: 1) are realistic (e.g., obstacle disrupting the foot in swing phase), 2) are unanticipated by subjects, 3) are controllable in their timing, and 4) allow for kinematic and kinetic evaluation.

Methods

A stumble perturbation system was designed that consists of an obstacle delivery apparatus that releases an obstacle onto a force-instrumented treadmill and a predictive targeting algorithm which controls the timing of the perturbation to the foot during swing phase. Seven healthy subjects were recruited to take part in an experimental protocol for system validation, which consisted of two sub-experiments. First, a perception experiment determined whether subjects could perceive the obstacle as it slid onto the treadmill belt. Second, a perturbation experiment assessed the timing accuracy of perturbations relative to a target percent swing input by the experimenter. Data from this experiment were then used to demonstrate that joint kinematics and kinetics could be computed before and after the perturbation.

Results

Out of 168 perception trials (24 per subject), not a single obstacle was perceived entering the treadmill by the subjects. Out of 196 perturbation trials, 190 trials successfully induced a stumble event, with a mean targeting accuracy, relative to the desired percent swing, of 25 ms (6.2% of swing phase). Joint kinematic and kinetic results were then computed for three common stumble recovery strategies and shown to be qualitatively consistent with results from prior stumble studies conducted overground.

Conclusions

The stumble perturbation system successfully introduced realistic obstacle perturbations that were unanticipated by subjects. The targeting accuracy substantially reduced mistrials (i.e., trials that did not elicit a stumble) compared to previous studies. This accuracy enables stumble recovery to be studied more systematically as a function of when the perturbation occurs during swing phase. Lastly, joint kinematic and kinetic estimates allow for a comprehensive analysis of stumble recovery biomechanics.