Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

Abstract

Stroke-induced hemiparetic gait is characteristically asymmetric and metabolically expensive. Weakness and impaired control of the paretic ankle contribute to reduced forward propulsion and ground clearance - walking subtasks critical for safe and efficient locomotion. Targeted gait interventions that improve paretic ankle function after stroke are therefore warranted. We have developed textile-based, soft wearable robots that transmit mechanical power generated by off-board or body-worn actuators to the paretic ankle using Bowden cables (soft exosuits) and have demonstrated the exosuits can overcome deficits in paretic limb forward propulsion and ground clearance, ultimately reducing the metabolic cost of hemiparetic walking. This study elucidates the biomechanical mechanisms underlying exosuit-induced reductions in metabolic power. We evaluated the relationships between exosuit-induced changes in the body center of mass (COM) power generated by each limb, individual joint power and metabolic power. Compared with walking with an exosuit unpowered, exosuit assistance produced more symmetrical COM power generation during the critical period of the step-to-step transition (22.4±6.4% more symmetric). Changes in individual limb COM power were related to changes in paretic (=0.83, 0.004) and non-paretic (0.73, 0.014) ankle power. Interestingly, despite the exosuit providing direct assistance to only the paretic limb, changes in metabolic power were related to changes in non-paretic limb COM power (=0.80, 0.007), not paretic limb COM power (0.05). These findings contribute to a fundamental understanding of how individuals post-stroke interact with an exosuit to reduce the metabolic cost of hemiparetic walking.

Powered ankle-foot orthoses: the effects of the assistance on healthy and impaired users while walking

“…Some studies that were performed with a soft exosuit providing ankle assistance on healthy and impaired users were included, due to the relevance of their findings with respect to the aspects discussed by this article. However, it is important to highlight that these devices also provide passive hip assistance along with active ankle assistance [ 22 – 27 ]. The rest of the paper is structured as follows: first, an overview of the developed PAFOs is given; then, the effects of the assistance provided by PAFOs on healthy and weakened users are compared and discussed.…”

Flexible Actuators for Soft Robotics

“…Copyright 2017, American Association for the Advancement of Science. d) A soft paretic ankle assistance exosuit developed by Bae et al Reproduced with permission . Copyright 2018, the Company of Biologists Ltd. e) A sensorized actuator fitted in a glove to achieve finger rehabilitation monitoring.…”

“…In contrast, robotic lower‐limb exoskeletons and orthoses can significantly improve the walking ability of patients suffering from stroke or spinal cord injuries (SCI) . For example, to develop walking rehabilitation and assistance robots with flexibility and portability, Bae et al . created a wearable robot based on textile, which transfers mechanical power from actuators to the paretic ankle and then cuts the metabolic cost of hemiparetic walking (Figure d).…”

Self-perceived functioning and disability after randomized conventional and electromechanically-assisted gait training in subacute stroke: A 6 months follow-up

“…This may be associated with an increased risk of musculoskeletal complications and falls, and increased energy expenditure in the long term [38]. Recently, interventions aiming at improving gait symmetry after stroke have been suggested [39][40][41] but are most often applied and evaluated in chronic stroke. Thus, studies with interventions targeting symmetrical walking in subacute stage after stroke to overcome these compensatory gait patterns are of great interest.…”

“…Gait interventions aiming at improving gait symmetry after stroke have recently been suggested [39][40][41] but most often been studied in chronic stroke. While the assessments in the clinic often report task accomplishment or time needed to perform a movement task, the use of a gait laboratory can reveal detailed information on how the task is performed or accomplished.…”