Robotic body weight support enables safe stair negotiation in compliance with basic locomotor principles

M Bannwart,M Bolliger,C A Easthope,E Rohland,G Rauter

doi:10.1186/s12984-019-0631-8

Abstract

BackgroundAfter a neurological injury, mobility focused rehabilitation programs intensively train walking on treadmills or overground. However, after discharge, quite a few patients are not able to independently negotiate stairs, a real-world task with high physical and psychological demands and a high injury risk. To decrease fall risk and improve patients’ capacity to navigate typical environments, early stair negotiation training can help restore competence and confidence in safe stair negotiation. One way to enable early training in a safe and permissive environment is to unload the patient with a body weight support system. We here investigated if unloaded stair negotiation complies with basic locomotor principles, in terms of enabling performance of a physiological movement pattern with minimal compensation.MethodsSeventeen able-bodied participants were unloaded with 0–50% bodyweight during self-paced ascent and descent of a 4-tread staircase. Spatio-temporal parameters, joint ranges of motion, ground reaction forces and myoelectric activity in the main lower limb muscles of participants were compared between unloading levels. Likelihood ratio tests of separated linear mixed models of the investigated outcomes assessed if unloading affects the parameters in general. Subsequent post-hoc testing revealed which levels of unloading differed from unsupported stair negotiation.ResultsUnloading affected walking velocity, joint ranges of motion, vertical ground reaction force parameters and myoelectric activity in all investigated muscles for stair ascent and descent while step width and single support duration were only affected during ascent. A reduction with increasing levels of body weight support was seen in walking velocity (0.07–0.12 m/s), ranges of motion of the knee and hip (2–10°), vertical ground reaction force peaks (10–70%) and myoelectric activity (17–70%). An increase with unloading was only seen during ascent for ankle range of motion and tibialis anterior activity at substantial unloading.ConclusionsBody weight support facilitates stair negotiation by providing safety and support against gravity. Although unloading effects are present in most parameters, up to 30% body weight support these changes are small, and no dysfunctional patterns are introduced. Body weight support therefore fulfills all the necessary requirements for early stair negotiation training.

Highlights

IntroductionMobility focused rehabilitation programs intensively train walking on treadmills or overground
After a neurological injury, mobility focused rehabilitation programs intensively train walking on treadmills or overground
Post-hoc tests confirm that velocity is reduced from baseline at all levels of Body weight support (BWS) except for the post measurement (Table 1)

Summary

Introduction

Mobility focused rehabilitation programs intensively train walking on treadmills or overground. A large proportion of modern rehabilitation programs focus on gait and balance training in compliance with locomotor training principles These principles are known to maximize recovery and restoration and state that weight-bearing through legs should be maximized, appropriate sensory cues and task-specific, physiological kinematics need to be provided while compensatory strategies should be minimized [4]. Robotic rehabilitation technology that assists training of stair negotiation from an early time point on is rare and limited to few devices such as end-effector-based gait trainers, ceiling-mounted BWS systems, and wearable exoskeletons [12,13,14,15,16,17]. BWS systems and wearable exoskeletons have the advantage that they allow training of real stair walking which helps provide the appropriate afferent sensory input to relearn the task. It is not clear if BWS hinders physiological performance of stair ambulation, something which must be first investigated in an able-bodied population

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