Walking Faster and Farther With a Soft Robotic Exosuit: Implications for Post-Stroke Gait Assistance and Rehabilitation

Abstract

Soft robotic exosuits can improve the mechanics and energetics of walking after stroke. Building on this prior work, we evaluated the effects of the first prototype of a portable soft robotic exosuit. Methods: Exosuit-induced changes in the overground walking speed, distance, and energy expenditure of individuals post-stroke were evaluated statistically and compared to minimal clinically important difference scores. Results: Compared to walking without the exosuit worn, the <5 kg exosuit did not substantially modify speed, distance, or energy expenditure when worn unpowered. In contrast, when powered on to provide an average 22.87 ± 0.58 %bodyweight of paretic plantarflexor force assistance during stance phase and assist the paretic dorsiflexors during swing phase to reduce drop-foot, study participants walked a median 0.14 ± 0.06 m/s faster during the 10-meter walk test and traveled 32 ± 8 m farther during the six minute walk test (P < 0.05). Conclusions: Individuals post-stroke can leverage the paretic plantarflexor and dorsiflexor assistance provided by soft robotic exosuits to achieve clinically-meaningful increases in speed and distance. INDEX TERMS Exosuit, soft robotics, propulsion, walking speed, walking distance, stroke. IMPACT STATEMENT Beyond improving the mechanics of post-stroke walking, exosuits facilitate faster and farther overground walking. These findings support the translation of the technology for both assistive and rehabilitative applications.

The ReWalk ReStore™ soft robotic exosuit: a multi-site clinical trial of the safety, reliability, and feasibility of exosuit-augmented post-stroke gait rehabilitation

“…This study builds on prior clinical, biomechanical, and physiological evaluations of soft robotic exosuits [19], demonstrating that, when used under the direction of a Unlike rigid exoskeletons that are powerful enough to move the limbs without user input [23,24], exosuitgenerated forces must work in synchrony with the user's movements to improve their walking. Given the stability deficits characteristic of the post-stroke population [14] and the potential for exosuit-generated forces to negatively perturb the user, an evaluation of the safety and reliability of clinicians operating the device during poststroke gait rehabilitation was necessary.…”

“…Together, these improvements in paretic limb function resulted in reduced propulsion asymmetry by 20% [17] and the asymmetry in positive COM power generated during late stance phase by 39% [18]. Also observed were immediate reductions in hip hiking and circumduction compensations of over 20% [9], reductions in the energy cost of walking by an average 10% [17,18], faster overground walking speeds by a median 0.14 m/s, and farther walking distances during the 6-min walk test by a median 32m [19].…”

“…Actual activities and durations were dependent on each study participant's abilities as determined by the treating physical therapist as per their usual practices. The target level for plantarflexion assistance during all active walking with the ReStore™ was 25% of the user's bodyweight [17,19]. The target level for dorsiflexion assistance was the minimum needed for adequate ground clearance and heel strike, as determined visually by the physical therapist.…”

“…It should be noted that this study's exploratory assessment of changes in speed was included to evaluate the therapeutic potential of using the ReStore™ as a rehabilitation robot in advance of future clinical efficacy trials. This study was not designed to assess immediate device efficacy (i.e., versus a no device control) as in previous studies of the exosuit technology that included individualized tuning of the assistance parameters and dedicated device exposure visits [9,17,19].…”

“…For the study, the target level for plantarflexion assistance was 100% (i.e., 25% of the wearer's bodyweight) and the target level for dorsiflexion assistance was the minimum needed for adequate ground clearance and heel strike, as determined visually by the physical therapist. See previous work [19] for visual depiction of the forces applied by the exosuit independent t-tests. Alpha was set to 0.05 for all analyses.…”