A multidirectional gravity-assist algorithm that enhances locomotor control in patients with stroke or spinal cord injury

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Science Translational Medicine  19 Jul 2017:
Vol. 9, Issue 399, eaah3621
DOI: 10.1126/scitranslmed.aah3621

Greater gait with gravity

Often taken for granted, gravity—the force that keeps you on the ground—becomes a notable challenge during rehabilitation from injury. Mignardot et al. “harnessed” gravity to test whether upward and forward forces, applied to the torso via a robotic body weight supportive device, assist with locomotion. Patients recovering from stroke or spinal cord injury demonstrated improved gait performance with the robotic harness. An important component of the gravity-assistive approach is an algorithm that adjusts the forces provided by the robotic harness according to the patient’s needs. Patients unable to walk without assistance (nonambulatory) were able to walk naturally with the harness, whereas ambulatory patients exhibited improved skilled locomotion such as balance, limb coordination, foot placement, and steering. A clinical trial using this robot-assistive rehabilitation approach for patients with spinal cord injury is currently under way.


Gait recovery after neurological disorders requires remastering the interplay between body mechanics and gravitational forces. Despite the importance of gravity-dependent gait interactions and active participation for promoting this learning, these essential components of gait rehabilitation have received comparatively little attention. To address these issues, we developed an adaptive algorithm that personalizes multidirectional forces applied to the trunk based on patient-specific motor deficits. Implementation of this algorithm in a robotic interface reestablished gait dynamics during highly participative locomotion within a large and safe environment. This multidirectional gravity-assist enabled natural walking in nonambulatory individuals with spinal cord injury or stroke and enhanced skilled locomotor control in the less-impaired subjects. A 1-hour training session with multidirectional gravity-assist improved locomotor performance tested without robotic assistance immediately after training, whereas walking the same distance on a treadmill did not ameliorate gait. These results highlight the importance of precise trunk support to deliver gait rehabilitation protocols and establish a practical framework to apply these concepts in clinical routine.

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