New exoskeleton therapy could redefine how stroke survivors relearn to walk

Physical therapists have long walked alongside stroke survivors during recovery. Now, they are walking with them.

Scientists at Northwestern University and Shirley Ryan AbilityLab have developed a first-of-its-kind rehabilitation system that virtually connects therapists and patients through robotic exoskeletons. The real-time connection allows therapists to respond to a patient’s movements, continuously adapting support and assistance as the patient’s performance evolves.

After training with the new system, patients moved their joints through a greater range of motion, took longer and higher steps and activated their muscles at levels similar to those seen with conventional therapy.

The study will be published on Wednesday (June 17) in the journal Science Robotics.

“Therapist-led rehabilitation remains the foundation of recovery for many patients, and this research shows promise for complementing this standard of care,” said José L. Pons, who conceptualized, led and supervised the research program.

Pons is a scientific chair at the Shirley Ryan AbilityLab, professor of physical medicine and rehabilitation at Northwestern University Feinberg School of Medicine and professor of mechanical engineering (by courtesy) at Northwestern’s McCormick School of Engineering. Other Northwestern coauthors include Daniel Ludvig, a research scientist at Shirley Ryan AbilityLab and research assistant professor at McCormick; Levi Hargrove, scientific chair of the Regenstein Foundation Center for Bionic Medicine at Shirley Ryan AbilityLab, professor of physical medicine and rehabilitation at Feinberg and professor of biomedical engineering (by courtesy) at McCormick; and Kevin Lynch, professor of mechanical engineering at McCormick and director of Northwestern’s Center for Robotics and Biosystems.

Each year, nearly 800,000 Americans survive a stroke, according to the Centers for Disease Control and Prevention. For many, the journey to recovery includes relearning one of life’s most fundamental activities: walking. Weakness, impaired coordination and reduced leg control can make even simple movements challenging. Recovery often requires months of intensive rehabilitation as patients work with physical therapists to regain mobility, independence and confidence.

In conventional physical therapy, therapists provide hands-on support and corrective guidance as patients walk. Because they can physically assist a limited number of movements at once, therapists often focus on a single aspect of gait. More complex, whole-body training can require multiple therapists. Meanwhile, rehabilitation exoskeletons can increase training intensity and help patients practice walking for longer periods of time, but many rely on fixed movement patterns that do not fully adapt to a patient’s performance in real time, limiting therapists’ ability to deliver personalized care.

To address these gaps, the Northwestern and Shirley Ryan AbilityLab team developed a novel intervention called therapist-exoskeleton-patient interaction (TEPI). Using TEPI, a therapist and stroke survivor each wear a lower-limb exoskeleton virtually connected at the hips and knees. The virtual connection behaves like a combination of springs and shock absorbers, allowing therapists and patients to influence each other’s movements in real time. The study demonstrated that therapists can effectively leverage TEPI to create more personalized rehabilitation experiences, supporting patients as they work toward recovery goals.

“By combining the hands-on adaptability of physical therapy with the scalability and precision of robotic systems, it can enable more comprehensive, whole-body gait training without requiring multiple therapists, while also introducing real-time responsiveness to patient-performance — allowing support, resistance and feedback to be adjusted dynamically,” said Lorenzo Vianello, a postdoctoral researcher at Shirley Ryan AbilityLab and a co-first author of the paper.

In evaluations with eight stroke survivors, TEPI outperformed conventional therapist-guided treadmill training on several measures of walking performance. Participants demonstrated great joint range of motion and took longer, higher seps while maintaining similar muscle activation. They also reported high levels of motivation and enjoyment.

“By allowing therapists to guide a patient’s movements through their own leg movements, TEPI could provide an impactful complement to conventional gait training for stroke rehabilitation, reducing physical effort that can contribute to fatigue and injury for therapists during hands-on therapy,” said the study’s co-first author Emek Barış Küçüktabak, who completed the research while a graduate research assistant at Northwestern University and Shirley Ryan AbilityLab.

Next, researchers plan to explore how this framework can be applied to other functionally relevant activities, such as overground walking, stair climbing and sit-to-stand transitions across multiple sessions of training. 

“Future work will also investigate more accessible and scalable systems that can extend therapist-guided rehabilitation into the home and support remote care,” said the study’s co-first author Matthew R. Short, a postdoctoral researcher at the University of Delaware.

The paper, “Therapist-Exoskeleton-Patient Interaction for Gait Therapy,” was supported by the National Science Foundation/National Robotics Initiative (award number 2024488).