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.

Background A higher energy cost of walking poststroke has been linked to reduced walking performance and reduced participation in the community. Objective To determine the contribution of post-intervention improvements in walking speed and spatiotemporal gait asymmetry to the reduction of the energy cost of walking after stroke. Methods Forty-two subjects with chronic hemiparesis (> 6 months poststroke) were recruited to participate in 12 weeks of walking rehabilitation. The energy cost of walking, walking speed, and step length, swing time, and stance time asymmetries were calculated pre- and posttraining. Sequential regression analyses tested the cross-sectional (ie, pretraining) and longitudinal (ie, posttraining changes) relationships between the energy cost of walking versus speed and each measure of asymmetry. Results Pretraining walking speed (β = −.506) and swing time asymmetry (β = .403) predicted pretraining energy costs (adjR2 = .713, F(3,37) = 34.05, p < .001). In contrast, change in walking speed (β = .340) and change in step length asymmetry (β = .934) predicted change in energy costs with a significant interaction between these independent predictors (adjR2 = .699, F(4,31) = 21.326, p < .001). Moderation by the direction or the magnitude of pretraining asymmetry was not found. Conclusions For persons in the chronic phase of stroke recovery, faster and more symmetric walking after intervention appears to be more energetically advantageous than merely walking faster or more symmetric. This finding has important functional implications given the relationship between the energy cost of walking and community walking participation.

OBJECTIVE To determine 1) the feasibility and safety of implementing a 12-week locomotor intervention targeting paretic propulsion deficits during walking through the joining of two independent interventions: walking at maximal speed on a treadmill and functional electrical stimulation of the paretic ankle musculature (FastFES), 2) the effects of FastFES training on individual subjects, and 3) the influence of baseline impairment severity on treatment outcomes. DESIGN A single group pre-post preliminary study investigating a novel locomotor intervention. Changes following treatment were assessed using pair-wise comparisons and compared to known minimal clinically important differences (MCIDs) or minimal detectable changes (MDCs). Correlation analyses were run to determine the relationship between baseline clinical and biomechanical performance versus improvements in walking speed. SETTING University clinical research laboratory. PARTICIPANTS Thirteen individuals with locomotor deficits following a stroke. INTERVENTION FastFES training was provided for 12 weeks at a frequency of 3 sessions per week and 30 minutes per session. MAIN OUTCOME MEASURES Measures of gait mechanics, functional balance, short- and long-distance walking function, and self-perceived participation were collected at baseline, post-training, and at a 3 month follow-up. RESULTS Twelve of the 13 subjects recruited completed training. Improvements in paretic propulsion were accompanied by improvements in functional balance, walking function, and self-perceived participation (each p < 0.02) – all of which were maintained at the 3 month follow up. Eleven of the 12 subjects achieved meaningful functional improvements. Baseline impairment was predictive of absolute, but not relative functional change following training. CONCLUSIONS This report demonstrates the safety and feasibility of the FastFES intervention and supports further study of this promising locomotor intervention for persons post-stroke.

Recent technological advancements have enabled the creation of portable, low-cost, and unobtrusive sensors with tremendous potential to alter the clinical practice of rehabilitation. The application of wearable sensors to movement tracking has emerged as a promising paradigm to enhance the care provided to patients with neurological or musculoskeletal conditions. These sensors enable quantification of motor behavior across disparate patient populations and emerging research shows their potential for identifying motor biomarkers, differentiating between restitution and compensation motor recovery mechanisms, remote monitoring, tele-rehabilitation, and robotics. Moreover, the big data recorded across these applications serve as a pathway to personalized and precision medicine. This paper presents state-of-the-art and next generation wearable movement sensors, ranging from inertial measurement units to soft sensors. An overview of clinical applications is presented across a wide spectrum of conditions that have potential to benefit from wearable sensors, including stroke, movement disorders, knee osteoarthritis, and running injuries. Complementary applications enabled by next-generation sensors that will enable point-of-care monitoring of neural activity and muscle dynamics during movement are also discussed.

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Background Recent rehabilitation efforts after stroke often focus on increasing walking speed because it is associated with quality of life. For individuals poststroke, propulsive force generated from the paretic limb has been shown to be correlated to walking speed. However, little is known about the relative contribution of the paretic versus the non-paretic propulsive forces to changes in walking speed. Objective The primary purpose of this study was to determine the contribution of propulsive force generated from each limb to changes in walking speed during speed modulation within a session and as a result of a 12-week training program. Methods Gait analysis was performed as participants (N=38) with chronic poststroke hemiparesis walked at their self-selected and faster walking speeds on a treadmill before and after a 12-week gait retraining program. Results Prior to training, stroke survivors increased non-paretic propulsive forces as the primary mechanism to change walking speed during speed modulation within a session. Following gait training, the paretic limb played a larger role during speed modulation within a session. In addition, the increases in paretic propulsive forces observed following gait training contributed to the increases in the self-selected walking speeds seen following training. Conclusions Gait retraining in the chronic phase of stroke recovery facilitates paretic limb neuromotor recovery and reduces the reliance on the non-paretic limb’s generation of propulsive force to increase walking speed. These findings support gait rehabilitation efforts directed toward improving the paretic limb’s ability to generate propulsive force.

Background Elucidation of the relative importance of commonly targeted biomechanical variables to poststroke long-distance walking function would facilitate optimal intervention design. Objectives To (1) determine the relative contribution of variables from three biomechanical constructs to poststroke long-distance walking and (2) identify the biomechanical changes underlying posttraining improvements in long-distance walking function. Methods Forty-four individuals > 6 months after stroke participated in this study. A subset of these subjects (n = 31) underwent 12 weeks of high-intensity locomotor training. Cross-sectional (pretraining) and longitudinal (posttraining change) regression quantified the relationships between poststroke long-distance walking function, as measured via the 6-Minute Walk Test (6MWT), and walking biomechanics. Biomechanical variables were organized into stance phase (paretic propulsion and trailing limb angle), swing phase (paretic ankle dorsiflexion and knee flexion), and symmetry (step length and swing time) constructs. Results Pretraining, all variables correlated with 6MWT distance (r’s = 0.39 to 0.75, p’s < 0.05); however, only propulsion (Prop) and trailing limb angle (TLA) independently predicted 6MWT distance (R2 = 0.655, F(6,36) = 11.38, p < .001). Interestingly, only ΔProp predicted Δ6MWT; however, pretraining Prop, pretraining TLA, and ΔTLA moderated this relationship (moderation model R2s = 0.383, 0.468, 0.289, respectively). Conclusions The paretic limb’s ability to generate propulsion during walking is a critical determinant of long-distance walking function after stroke. This finding supports the development of poststroke interventions that impact deficits in propulsion and trailing limb angle.

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.