A biomechanical comparison of powered robotic exoskeleton gait with normal and slow walking: An investigation with able-bodied individuals

Abstract

BackgroundOverground lower-limb robotic exoskeletons are assistive devices used to facilitate ambulation and gait rehabilitation. Our understanding of how closely they resemble comfortable and slow walking is limited. This information is important to maximise the effects of gait rehabilitation. The aim was to compare the 3D gait parameters of able-bodied individuals walking with and without an exoskeleton at two speeds (self-selected comfortable vs. slow, speed-matched to the exoskeleton) to understand how the user's body moved within the device. MethodsEight healthy, able-bodied individuals walked along a 12-metre walkway with and without the exoskeleton. Three-dimensional whole-body kinematics inside the device were captured. Temporal-spatial parameters and sagittal joint kinematics were determined for normal and exoskeleton walking. One-way repeated measures ANOVAs and statistical parametric mapping were used to compare the three walking conditions ( P <0.05). FindingsThe walking speeds of the slow (0.44[0.03] m/s) and exoskeleton (0.41[0.03] m/s) conditions were significantly slower than the comfortable walking speed (1.54[0.07] m/s). However, time in swing was significantly greater ( P <0.001, d =-3.64) and double support was correspondingly lower ( P <0.001, d =3.72) during exoskeleton gait than slow walking, more closely resembling comfortable speed walking. Ankle and knee angles were significantly reduced in the slow and exoskeleton conditions. Angles were also significantly different for the upper body. InterpretationAlthough the slow condition was speed-matched to exoskeleton gait, the stance:swing ratio of exoskeleton stepping more closely resembled comfortable gait than slow gait. The altered upper body kinematics suggested that overground exoskeletons may provide a training environment that would also benefit balance training.

Biomechanical differences between able-bodied and spinal cord injured individuals walking in an overground robotic exoskeleton

“…Based on the motor learning principles of repetition, specificity and problem solving [ 16 – 18 ] robotic exoskeletons present an opportunity to facilitate gait re-education and provide the desired afferent feedback to activate CPGs. Previous work has compared exoskeleton walking in the ReWalk TM (ARGO Medical Technologies Ltd., Yokneam, Israel) with speed-matched (SLOW) and preferred speed (NORM) walking in the same group of able-bodied individuals [ 19 ]. It was found that the temporal components of exoskeleton gait more closely resembled NORM walking as opposed to SLOW walking whereas the spatial components of exoskeleton gait resembled SLOW gait [ 19 ].…”

“…Previous work has compared exoskeleton walking in the ReWalk TM (ARGO Medical Technologies Ltd., Yokneam, Israel) with speed-matched (SLOW) and preferred speed (NORM) walking in the same group of able-bodied individuals [ 19 ]. It was found that the temporal components of exoskeleton gait more closely resembled NORM walking as opposed to SLOW walking whereas the spatial components of exoskeleton gait resembled SLOW gait [ 19 ]. The SLOW condition allowed biomechanical differences between able-bodied gait and exoskeleton gait to be identified independent of speed, leading to the conclusion that complex upper body postural control was a significant factor related to balance and continuous stepping in the exoskeleton condition [ 19 ].…”

“…It was found that the temporal components of exoskeleton gait more closely resembled NORM walking as opposed to SLOW walking whereas the spatial components of exoskeleton gait resembled SLOW gait [ 19 ]. The SLOW condition allowed biomechanical differences between able-bodied gait and exoskeleton gait to be identified independent of speed, leading to the conclusion that complex upper body postural control was a significant factor related to balance and continuous stepping in the exoskeleton condition [ 19 ]. In “normal” able-bodied gait, maintaining dynamic balance is achieved through the anterio-lateral placement of the swinging limb to the falling centre of mass (COM) [ 20 , 21 ].…”

“…The fourth and final objective was to compare the ground reaction forces (GRF) of the two groups. Previous work has demonstrated that the GRFs of able-bodied individuals during exoskeleton gait were significantly lower than NORM walking and that they resembled SLOW gait GRFs [ 19 ]. As the walking speed of SCI and able-bodied users should be the same, speed-related differences in GRF profiles were not anticipated.…”

Adaptation Strategies for Personalized Gait Neuroprosthetics

“…The effectiveness of gait neuroprostheses can be quantitatively assessed by measuring the gait speed, where desired gait speeds suitable for community use are between 0.8 and 1.2 m/s (Robinett and Vondran, 1988 ; Lapointe et al, 2001 ), or by measuring the metabolic energy expenditure while using the device (Asselin et al, 2015 ; Evans et al, 2015 ; Miller et al, 2016 ). Other acceptable metrics could be gait outcomes such as kinematics or symmetry (Hayes et al, 2020 ). Furthermore, limits for comfortable and tolerable stimulation should be defined for each user.…”