It is believed that over 80 per cent of stroke survivors experience gait challenge, often associated with loss of control over ankle movement.
Researchers believe that an ‘agile, untethered, and easy-to-use ankle exosuit’ could help tackle this issue.
This exosuit is designed for independent use in a public environment, the exosuit also promises to help stroke survivors improve their gait outside of the lab and during their daily routines.
The study
A proof-of-concept study has shown that the community-use ankle exosuit could help stroke survivors improve their walking propulsion and boost their overall walking confidence and ability while ambulating around their own homes, workplaces, and neighbourhoods.
Previous studies have shown that stroke survivor study participants can improve their walking speed, distance covered, propulsion, and gait symmetry with the help of an assistive robotic exosuit, but those studies have all taken place in labs or clinical settings.
Conor Walsh, senior author of the study, says: “We saw an opportunity to leverage wearable technology to rethink how we approach physical therapy and rehabilitation.
“If we can shift some of these clinical services from the clinic to the home and community, we can improve access, reduce costs and deliver better care. It is exciting to see the fields of engineering and physical therapy come together to make this happen.”
This study was led by Conor Walsh’s team at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).
Co-first author of the study, Richard Nuckols, says: “In the past, our ankle exosuits had two active actuators – one that helped with dorsiflexion to keep the wearer’s toes up, and another to help with plantarflexion, propelling the foot and body away from the ground.”
Instead of an active dorsiflexion actuator, the new exosuit contains a passive material that flexes and performs like a spring, helping the toes stay up during the foot’s swing phase and preventing the wearer from catching their toes on the ground.
Nuckols, says: “By replacing an active actuator with a passive actuator, the exosuit is inherently safer; in the case of an unexpected power loss or controller failure, the default state will keep the users toes up and reduce risk of a trip and fall.”
Chih-Kang Chang, also co-first author, says: “We also developed a mobile app to enable wearers to easily interact with the device and remotely check in with our team.
“The app allows wearers to turn the device on themselves and tell the exosuit when they want to start walking.”
By adding sensors to the exosuit, the team have made it possible for remote monitoring of the wearer’s progress over time. Chang, says: ”We are collecting data while people are walking in the exosuit, and measuring how they improve their gait over time.
“Going forward, this information could be a really powerful aspect of using this exosuit for long-term rehabilitation in partnership with a physical therapist.”
Nuckols adds to this point, saying: “These sensors – located on the foot, shank, and pelvis – are converted using a machine-learning algorithm into estimates of propulsion, helping us understand how well people are generating proper ankle mechanics and how effectively they are walking.
Challenges faced
On the challenges face throughout this study, Daekyum Kim, also co-first author of the study, says: “Collecting the amount of data needed to train a typical machine learning model from individual wearers is extremely challenging, given the limited ability to walk for extended periods of time post-stroke.
“The key advantage of our approach is that it leverages walking data gathered from multiple individuals to better tune a machine learning model to each user.”
Recruiting participants
In order to test the community ankle exosuit, Walsh’s team partnered with the labs of Lou Awad and Terry Ellis from Boston University’s Sargent College of Health & Rehabilitation Sciences.
Four participants were recruited to use the device in their own community settings for four weeks, walking independently three to five times each week. All participants safely completed the study and reported no safety issues.
Due to individual variability in response (participants with lower baseline walking propulsion saw more benefit from wearing the exosuit), therapeutic benefit was not observed across the whole group.
However, two of the participants improved their propulsion by an average of 27 per cent. They also walked an average of 4,000 steps further in the week after the study than they had walked in the week before the start of the study.
Participant feedback
Bryant Butler, 51, study participant, says: “I was 33 when I had my stroke. As a result of the stroke, I have diminished sensitivity on my entire left side.
“Walking is a challenge. I can’t feel my toes very well when I am walking, and I have difficulty bending my leg. I frequently scuff the toe of my shoe, and sometimes I trip.
“The experience of walking with the exosuit was liberating, because I no longer had to expend so much mental energy when going from one place to another.
“The exosuit gradually corrected my gait with every step. I learned how my leg muscles, knee, and toes should feel when I walk without it. [Even] when I wasn’t using [the exosuit], my walking improved, because the device taught me how to better compensate for the shortcomings of my left leg post-stroke.
“The device became an extra piece of clothing – [except for the] wires and a battery pack – that I wore for a specific purpose. Most of the time, I forgot it was there. The exosuit nudged me into being a better walker. It inspired me to walk more, and to enjoy it.”
