More than 80% of stroke survivors experience gait problems, often associated with loss of ankle control. Existing rehabilitation devices to combat this problem are limited to laboratory or clinical settings. 

Now, according to a pilot study, a new ankle exosuit could help stroke survivors improve their walking ability. The work, led by the team of Professor Conor Walsh of the John A. Paulson School of Engineering and Applied Sciences (SEAS), has been published in the Annals of the New York Academy of Sciences. 

“We saw an opportunity to use wearable technology to rethink the approach to physical therapy and rehabilitation,” says Walsh. “If we can move some of these clinical services from the clinic to the home and community, we can improve access, reduce costs, and provide better care. Very It's exciting to see how engineering and physiotherapy come together to make this happen." 

The Walsh Biodesign Lab at Harvard has previously developed assistive and rehabilitation exosuit technologies for a variety of applications. Some of these technologies have already been licensed and commercialized by ReWalk Robotics and have received breakthrough status from the US Food and Drug Administration. To develop an ankle-foot exosuit for everyday use, Walsh's team needed to simplify the exosuit's mechanical components and make it easy to control. 

“In the past, our ankle exosuits had two active actuators—one assisted in dorsiflexion to hold the toes, and the other assisted in plantarflexion by pushing the foot and body off the ground,” says Richard Nuckols, a former Walsh lab postdoctoral fellow at SEAS. “Instead of active actuator dorsiflexion, the new exosuit contains a passive material that flexes and acts like a spring, helping to keep the toes up during the footswing and preventing the wearer from getting their toes caught on the ground." 

"By replacing the active drive with a passive drive, the exosuit is inherently safer; in the event of an unexpected power loss or controller failure, the default state will support the user's toes and reduce the risk of trips and falls," Nakols continues. 

"We also developed a mobile app so that users can easily interact with the device," says Chi-Kang Chang, Ph.D. at the Walsh Lab. "The app allows users to turn on the device themselves and tell the exosuit when they want to start walking." 

In addition, the team included sensors located on the foot, lower leg and pelvis to enable remote monitoring of the user's progress over time. 

“We collect data while people are walking in the exosuit and measure how their gait improves over time,” Chang says. “In the future, this information could be a really important aspect of using this exosuit for long-term rehabilitation in collaboration with a physical therapist.” 

To test the exosuit, Walsh's team collaborated with the labs of Lou Awad and Terry Ellis at Boston University's Sargent College of Health and Rehabilitation. They recruited four participants to use the device in their own setting for 4 weeks, walking 3-5 times a week on their own. 

Due to individual variability in response (participants with lower baseline walking activity benefited more from wearing the exosuit), a therapeutic effect was not observed in the entire group. But two of the participants improved their motor activity by an average of 27%. They also walked an average of 4,000 more steps the week after the study than they did the week before.