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Learning to walk in rehabilitation

Harvard study suggests improvements for clinical exoskeletons

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A study into rehabilitation robots used to teach patients to walk again demonstrates that these robots are failing to help patients alter the height of their steps. The researchers suggest that clinical robots would be more effective if they do more to threaten stability.

Patients recovering from spinal cord injuries, strokes or other conditions require months of therapy as they gradually learn to walk again.

They can be helped with robotic exoskeletons, often called Step Rehabilitation Robots. These moveable, wearable machines support the body, and apply force to the different parts of the lower body to encourage movement, and eventually build up strength, technique and endurance.

These exoskeletons aim to help lengthen stride, increase step height, bend the knees and toes and straighten the hips.

The study, conducted at the Wyss Institute for Biologically Inspired Engineering at Harvard University, demonstrated that these clinical robotic suits only help patients learn to walk again when they apply a force to threaten stability.

The researchers measured how the gait of patients on a treadmill changed in response to an exoskeleton applying different types of force.

While patients respond to changes in step length while wearing clinical robotic suits, they fail to modify their step height, even when height and length were ‘prodded’ at the same time. They suggest that this is due to the reliance of the central nervous system on stability in adjusting to disruptions in normal walking.

“Lifting your foot higher mid-stride doesn’t really make you that much less stable, whereas placing your foot closer or further away from your centre of mass can really throw off your balance, so the body adjusts much more readily to that disturbance,” said Dr Giacomo Severini, an author of the study.

“The results of our study give us insight into the way people adapt to external forces while walking in general, which is useful for clinicians when evaluating whether their patients will respond to clinical robot interventions,” says Professor Bonato, lead author and an associate professor at Harvard Medical School.

In order to adjust the height of step and angle of the toes while learning to walk again, patients may require treatment beyond walking with a standard clinical exoskeleton. The researchers suggest that customising clinical exoskeletons to apply forces to threaten stability relating to step height more severely could help rehabilitation.

“As the human population ages, robotics is playing an increasing role in their care and treatment,” said Professor Donald Ingber, founding director of the Wyss Institute. “Studying how the human body interacts with robots can not only teach us how to build better clinical rehabilitation machines, but also how our own human bodies work.”

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