Harvard SEAS ankle exosuit image

A study at Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) in the US is looking at how an ankle exosuit could give post-stroke wearers more independence in the community by improving their gait.

Key study outcomes included improved gait propulsion and an increase in daily steps from wearing the rehabilitation device.

While the ankle exosuit is used in the US, the observations and outcomes of the study are still relevant to the UK when looking at improving gait among post-stroke survivors.

In the UK, Stroke Association data reveals that 100,000 people have strokes each year. A stroke occurs every five minutes. While the UK Government notes that stroke is a leading cause of death and disability in the UK.

Research also reveals that nearly three-quarters of stroke survivors in the UK have leg weakness, and over three-quarters have arm weakness. This can lead to gait challenges among stroke survivors, meaning that walking can be difficult.

However, SEAS is hoping to tackle this with its agile, untethered, and easy-to-use ankle exosuit.

Designed for independent use in community settings, the assistive technology could help stroke survivors improve their gait outside of the lab and during their daily routines. A proof-of-concept study suggests the 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.

The work, led by Conor Walsh’s team at SEAS, is published online in Annals of the New York Academy of Sciences.

See the ankle exosuit in action in the video below.

 The idea is that the device is used in a ‘real-world’ scenario, as opposed to benefits being observed in a lab or clinical settings.

“We saw an opportunity to leverage wearable technology to rethink how we approach physical therapy and rehabilitation,” explained Conor, the senior author on the paper and Paul A. Maeder Professor of Engineering and Applied Sciences at SEAS. “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.”

To ensure the device was suitable for community settings, Conor’s team needed to simplify the exosuit’s mechanical components and make it easy for wearers to control.

“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,” commented Richard Nuckols, a former postdoctoral fellow in Conor’s lab at SEAS and a co-first author of the paper.

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.

“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,” added Richard.

There is also an accompanying mobile app for wearers to easily interact with the rehabilitation technology and remotely check in with the SEAS team. Users can turn on their device via the app and tell the exosuit they want to start walking.

In addition, the team incorporated sensors to allow for remote monitoring of the wearer’s gait progress over time. This information could be very helpful for long-term rehabilitation, as clinicians can easily monitor the wearer’s improvements.

To test the ankle exosuit, Conor’s team partnered with the labs of Lou Awad and Terry Ellis from Boston University College of Health & Rehabilitation Sciences: Sargent College.

The BU team recruited four participants 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 percent. 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.

Currently, researchers from Lancaster University are looking at how performance capture technology used in Hollywood films could be used to aid treatment and rehabilitation for stroke patients. Learn more here.

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