Jaehyun Bae

Biomechanical and Physiological Evaluation of Multi-Joint Assistance With Soft Exosuits

To understand the effects of soft exosuits on human loaded walking, we developed a reconfigurable multi-joint actuation platform that can provide synchronized forces to the ankle and hip joints. Two different assistive strategies were evaluated on eight subjects walking on a treadmill at a speed of 1.25 m/s with a 23.8 kg backpack: 1) hip extension assistance and 2) multi-joint assistance (hip extension, ankle plantarflexion and hip flexion). Results show that the exosuit introduces minimum changes to kinematics and reduces biological joint moments. A reduction trend in muscular activity was observed for both conditions. On average, the exosuit reduced the metabolic cost of walking by

A soft robotic exosuit improves walking in patients after stroke

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A soft exosuit for patients with stroke: Feasibility study with a mobile off-board actuation unit

and

Reducing Circumduction and Hip Hiking During Hemiparetic Walking Through Targeted Assistance of the Paretic Limb Using a Soft Robotic Exosuit

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

for hip extension assistance and multi-joint assistance respectively, which is equivalent to an average metabolic reduction of 4.6% and 14.6%, demonstrating that soft exosuits can effectively improve human walking efficiency during load carriage without affecting natural walking gait. Moreover, it indicates that actuating multiple joints with soft exosuits provides a significant benefit to muscular activity and metabolic cost compared to actuating single joint.

O 089 - A soft robotic exosuit assisting the paretic ankle in patients post-stroke: Effect on muscle activation during overground walking

Soft exosuits facilitate more normal walking after stroke. A softer recovery after stroke Passive assistance devices such as canes and braces are often used by people after stroke, but mobility remains limited for some patients. Awad et al. studied the effects of active assistance (delivery of supportive force) during walking in nine patients in the chronic phase of stroke recovery. A soft robotic exosuit worn on the partially paralyzed lower limb reduced interlimb propulsion asymmetry, increased ankle dorsiflexion, and reduced the energy required to walk when powered on during treadmill and overground walking tests. The exosuit could be adjusted to deliver supportive force during the early or late phase of the gait cycle depending on the patient’s needs. Although long-term therapeutic studies are necessary, the immediate improvement in walking performance observed using the powered exosuit makes this a promising approach for neurorehabilitation. Stroke-induced hemiparetic gait is characteristically slow and metabolically expensive. Passive assistive devices such as ankle-foot orthoses are often prescribed to increase function and independence after stroke; however, walking remains highly impaired despite—and perhaps because of—their use. We sought to determine whether a soft wearable robot (exosuit) designed to supplement the paretic limb’s residual ability to generate both forward propulsion and ground clearance could facilitate more normal walking after stroke. Exosuits transmit mechanical power generated by actuators to a wearer through the interaction of garment-like, functional textile anchors and cable-based transmissions. We evaluated the immediate effects of an exosuit actively assisting the paretic limb of individuals in the chronic phase of stroke recovery during treadmill and overground walking. Using controlled, treadmill-based biomechanical investigation, we demonstrate that exosuits can function in synchrony with a wearer’s paretic limb to facilitate an immediate 5.33 ± 0.91° increase in the paretic ankle’s swing phase dorsiflexion and 11 ± 3% increase in the paretic limb’s generation of forward propulsion (P < 0.05). These improvements in paretic limb function contributed to a 20 ± 4% reduction in forward propulsion interlimb asymmetry and a 10 ± 3% reduction in the energy cost of walking, which is equivalent to a 32 ± 9% reduction in the metabolic burden associated with poststroke walking. Relatively low assistance (~12% of biological torques) delivered with a lightweight and nonrestrictive exosuit was sufficient to facilitate more normal walking in ambulatory individuals after stroke. Future work will focus on understanding how exosuit-induced improvements in walking performance may be leveraged to improve mobility after stroke.

Assistive flexible suits, flexible suit systems, and methods for making and control thereof to assist human mobility

In this paper, we present the first application of a soft exosuit to assist walking after stroke. The exosuit combines textile garments with cable driven actuators and is lighter and more compliant as compared to traditional rigid exoskeletons. By avoiding the use of rigid elements, exosuits offer greater comfort, facilitate donning/doffing, and do not impose kinematic restrictions on the wearer - all while retaining the ability to generate significant moments at target joints during walking. The stroke-specific exosuit adapted from previous exosuit designs provides unilateral assistance to the paretic limb during walking. This paper describes stroke-specific design considerations, the design of the textile components, the development of a research-focused, mobile off-board actuation unit capable of testing the exosuit in a variety of walking conditions, a real-time gait detection and control algorithm, and proof-of-principle data validating the use of the exosuit in the chronic stroke population. Ultimately, we demonstrate reliable tracking of poststroke gait, appropriate timing of assistive forces, and improvements in key gait metrics. These preliminary results demonstrate the feasibility and promise of exosuits for poststroke gait assistance and training. Future work will involve the creation of a portable, body-worn system based on the specifications obtained from such feasibility studies that will enable community-based rehabilitation.

A Lightweight and Efficient Portable Soft Exosuit for Paretic Ankle Assistance in Walking After Stroke

Objective The aim of the study was to evaluate the effects on common poststroke gait compensations of a soft wearable robot (exosuit) designed to assist the paretic limb during hemiparetic walking. Design A single-session study of eight individuals in the chronic phase of stroke recovery was conducted. Two testing conditions were compared: walking with the exosuit powered versus walking with the exosuit unpowered. Each condition was 8 minutes in duration. Results Compared with walking with the exosuit unpowered, walking with the exosuit powered resulted in reductions in hip hiking (27 [6%], P = 0.004) and circumduction (20 [5%], P = 0.004). A relationship between changes in knee flexion and changes in hip hiking was observed (Pearson r = −0.913, P < 0.001). Similarly, multivariate regression revealed that changes in knee flexion (&bgr; = −0.912, P = 0.007), but not ankle dorsiflexion (&bgr; = −0.194, P = 0.341), independently predicted changes in hip hiking (R2 = 0.87, F(2, 4) = 13.48, P = 0.017). Conclusions Exosuit assistance of the paretic limb during walking produces immediate changes in the kinematic strategy used to advance the paretic limb. Future work is necessary to determine how exosuit-induced reductions in paretic hip hiking and circumduction during gait training could be leveraged to facilitate more normal walking behavior during unassisted walking.

Soft exosuits increase walking speed and distance 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 (R2=0.83, P=0.004) and non-paretic (R2=0.73, P=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 (R2=0.80, P=0.007), not paretic limb COM power (P>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. Summary: A soft robotic exosuit designed to assist the paretic limb during walking can induce more symmetrical body center of mass power generation by the paretic and non-paretic limbs and reduce metabolic power consumption during hemiparetic walking.

Exosuit-induced improvements in walking after stroke: Comprehensive analysis on gait energetics and biomechanics

This study compared overground walking with and without exosuit assistance in post-stroke patients. Exosuit-assisted walking was found to improve paretic propulsion and ground clearance during swing, two common gait deviations in stroke patients. No changes in leg muscle activity was found, motivating further study of the exosuit as a tool for gait training during stroke rehabilitation.