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1. Real-time gait metric estimation for everyday gait training with wearable devices in people poststroke

   https://doi.org/10.1017/wtc.2020.11  

   Arens, Philipp ; Siviy, Christopher ; Bae, Jaehyun ; Choe, Dabin K. ; Karavas, Nikos ; Baker, Teresa ; Ellis, Terry D. ; Awad, Louis N. ; Walsh, Conor J. ( January 2021 , Wearable Technologies)

   null (Ed.)

   Abstract Hemiparetic walking after stroke is typically slow, asymmetric, and inefficient, significantly impacting activities of daily living. Extensive research shows that functional, intensive, and task-specific gait training is instrumental for effective gait rehabilitation, characteristics that our group aims to encourage with soft robotic exosuits. However, standard clinical assessments may lack the precision and frequency to detect subtle changes in intervention efficacy during both conventional and exosuit-assisted gait training, potentially impeding targeted therapy regimes. In this paper, we use exosuit-integrated inertial sensors to reconstruct three clinically meaningful gait metrics related to circumduction, foot clearance, and stride length. Our method corrects sensor drift using instantaneous information from both sides of the body. This approach makes our method robust to irregular walking conditions poststroke as well as usable in real-time applications, such as real-time movement monitoring, exosuit assistance control, and biofeedback. We validate our algorithm in eight people poststroke in comparison to lab-based optical motion capture. Mean errors were below 0.2 cm (9.9%) for circumduction, −0.6 cm (−3.5%) for foot clearance, and 3.8 cm (3.6%) for stride length. A single-participant case study shows our technique’s promise in daily-living environments by detecting exosuit-induced changes in gait while walking in a busy outdoor plaza. 

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2. Ankle-targeted exosuit resistance increases paretic propulsion in people post-stroke

   https://doi.org/10.1186/s12984-023-01204-w  

   Swaminathan, Krithika ; Porciuncula, Franchino ; Park, Sungwoo ; Kannan, Harini ; Erard, Julien ; Wendel, Nicholas ; Baker, Teresa ; Ellis, Terry D. ; Awad, Louis N. ; Walsh, Conor J. ( June 2023 , Journal of NeuroEngineering and Rehabilitation)

   Individualized, targeted, and intense training is the hallmark of successful gait rehabilitation in people post-stroke. Specifically, increasing use of the impaired ankle to increase propulsion during the stance phase of gait has been linked to higher walking speeds and symmetry. Conventional progressive resistance training is one method used for individualized and intense rehabilitation, but often fails to target paretic ankle plantarflexion during walking. Wearable assistive robots have successfullyassistedankle-specific mechanisms to increase paretic propulsion in people post-stroke, suggesting their potential to provide targetedresistanceto increase propulsion, but this application remains underexamined in this population. This work investigates the effects of targeted stance-phase plantarflexion resistance training with a soft ankle exosuit on propulsion mechanics in people post-stroke.

   We conducted this study in nine individuals with chronic stroke and tested the effects of three resistive force magnitudes on peak paretic propulsion, ankle torque, and ankle power while participants walked on a treadmill at their comfortable walking speeds. For each force magnitude, participants walked for 1 min while the exosuit was inactive, 2 min with active resistance, and 1 min with the exosuit inactive, in sequence. We evaluated changes in gait biomechanics during the active resistance and post-resistance sections relative to the initial inactive section.

   Walking with active resistance increased paretic propulsion by more than the minimal detectable change of 0.8 %body weight at all tested force magnitudes, with an average increase of 1.29 ± 0.37 %body weight at the highest force magnitude. This improvement corresponded to changes of 0.13 ± 0.03 N m kg^− 1in peak biological ankle torque and 0.26 ± 0.04 W kg^− 1in peak biological ankle power. Upon removal of resistance, propulsion changes persisted for 30 seconds with an improvement of 1.49 ± 0.58 %body weight after the highest resistance level and without compensatory involvement of the unresisted joints or limb.

   Targeted exosuit-applied functional resistance of paretic ankle plantarflexors can elicit the latent propulsion reserve in people post-stroke. After-effects observed in propulsion highlight the potential for learning and restoration of propulsion mechanics. Thus, this exosuit-based resistive approach may offer new opportunities for individualized and progressive gait rehabilitation.

    

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3. Design and evaluation of an independent 4‐week, exosuit‐assisted, post‐stroke community walking program

   https://doi.org/10.1111/nyas.14998  

   Nuckols, Richard W. ; Chang, Chih‐Kang ; Kim, Daekyum ; Eckert‐Erdheim, Asa ; Orzel, Dorothy ; Baker, Lauren ; Baker, Teresa ; Wendel, Nicholas C. ; Quinlivan, Brendan ; Murphy, Patrick ; et al ( May 2023 , Annals of the New York Academy of Sciences)

   Chronic impairment in the paretic ankle following stroke often requires that individuals use compensatory patterns such as asymmetric propulsion to achieve effective walking speeds needed for community engagement. Ankle exosuit assistance can provide ankle biomechanical benefit in the lab, but such environments inherently limit the amount of practice available. Community walking studies without exosuits can provide massed practice and benefit walking speed but are limited in their ability to assist proper mechanics. In this study, we combined the positive aspects of community training with those of exosuit assistance. We developed and evaluated a community Robotic Exosuit Augmented Locomotion (cREAL) program. Four participants in the chronic stage of stroke independently used our community ankle exosuit for walking in the community 3–5 days/week for 4 weeks. We performed lab evaluations before and after the 4‐week program. Two participants significantly improved their unassisted paretic propulsion by an average of 27% after the program and walked on average 4001 steps/day more in the week following the program. Despite the small number of participants, this study provides preliminary evidence for the potential of exosuits to augment gait training and rehabilitation in the community.

    

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4. Extremum Seeking Control of a Robotic Ankle-Foot Orthosis Targeting the Soleus Muscle Activation During Walking

   https://doi.org/10.1109/CCTA60707.2024.10666517  

   Tulsky, Evan ; Rubino, Nicholas ; Carter, Jade ; Thompson, Aiko K ; Duenas, Victor H ( August 2024 , IEEE)

   Stroke survivors experience muscle weakness and low weight-bearing capacity that impair their walking. The activation of the plantarflexor muscles is diminished following a stroke, which degrades propulsion and balance. Powered exoskeletons can improve gait capacity and restore impaired muscle activity. However, a technical barrier exists to generate systematic control methods to predictably and safely perturb the paretic leg using a wearable device to characterize the plantarflexors’ muscle output for gait training. In this paper, a closed-loop robust controller is designed to impose an ankle joint rotation (i.e., a kinematic perturbation) in the mid-late stance phase to target the soleus muscle using a powered cable-driven ankle-foot orthosis. The goal is to generate soleus muscle activity increments throughout a gait experiment by applying ankle perturbations. This ability to modulate plantarflexor activity can be used in future conditioning studies to improve push-off and propulsion during walking. However, the optimal perturbation magnitude for each participant is unknown. Hence, online adaptation of the ankle perturbation is well-motivated to modulate the soleus response measured using surface electromyography (EMG). An extremum seeking controller (ESC) is implemented in real-time to compute the ankle perturbation magnitude (i.e., dorsiflexion angle) exploiting the soleus EMG response from the previous perturbed step to maximize the soleus response in the next perturbed step. A Lyapunov-based stability analysis is used to guarantee exponential kinematic tracking of the ankle perturbation objective. 

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5. The Treadport: Natural Gait on a Treadmill

   https://doi.org/10.1177/0018720818819951  

   Chesebrough, Sam ; Hejrati, Babak ; Hollerbach, John ( January 2019 , Human Factors: The Journal of the Human Factors and Ergonomics Society)

   To evaluate the differences between walking on an advanced robotic locomotion interface called the Treadport and walking overground with healthy subjects.

   Previous studies have compared treadmill-based and overground walking in terms of gait parameters. The Treadport’s unique features including self-selected speed capability, large belt, kinesthetic force feedback, and virtual reality environment distinguish it from other locomotion interfaces and could provide a natural walking experience for the users.

   Young, healthy subjects ( N = 17) walked 10 meters 10 times each for both overground and the Treadport environments. Comparison between walking conditions used spatiotemporal and kinematic parameters. In addition, electromyographic data was collected for five of the 17 subjects to compare muscle activity between the two conditions.

   Gait on the Treadport was found to have no significant differences ( p > .05) with overground walking in terms of hip and knee joint angles, cadence and stride length and stride speed, and muscle activation of the four muscle groups measured. Differences ( p < .05) were observed in ankle dorsiflexion which was reduced by 2.47 ± 0.01 degrees on the Treadport.

   Walking overground and on the Treadport is highly correlated and not significantly different in 13 of 14 parameters.

   This study suggests that the Treadport creates an environment for natural walking experience, where natural gait of users is almost preserved, with great potential to be useful for other applications, such as gait rehabilitation of individuals with walking impairments.

    

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