Ankle training with a robotic device improves hemiparetic gait after a stroke

Abstract

Background: Task-oriented therapies such as treadmill exercise can improve gait velocity after stroke, but slow velocities and abnormal gait patterns often persist, suggesting a need for additional strategies to improve walking.

Objectives: To determine the effects of a 6-week visually guided, impedance controlled, ankle robotics intervention on paretic ankle motor control and gait function in chronic stroke.

Methods: This was a single-arm pilot study with a convenience sample of 8 stroke survivors with chronic hemiparetic gait, trained and tested in a laboratory. Subjects trained in dorsiflexion-plantarflexion by playing video games with the robot during three 1-hour training sessions weekly, totaling 560 repetitions per session. Assessments included paretic ankle ranges of motion, strength, motor control, and overground gait function.

Results: Improved paretic ankle motor control was seen as increased target success, along with faster and smoother movements. Walking velocity also increased significantly, whereas durations of paretic single support increased and double support decreased.

Conclusions: Robotic feedback training improved paretic ankle motor control with improvements in floor walking. Increased walking speeds were comparable with reports from other task-oriented, locomotor training approaches used in stroke, suggesting that a focus on ankle motor control may provide a valuable adjunct to locomotor therapies.

Conflict of interest statement

Declaration of Conflicting Interests

The author(s) declared a potential conflict of interest (e.g. a financial relationship with the commercial organizations or products discussed in this article) as follows: Dr. H. I. Krebs is a co-inventor in the MIT patents for the robotic devices. He holds equity positions in Interactive Motion Technologies, Inc., the company that manufactures this type of technology under license to MIT.

Figures

Figure 1. The anklebot is depicted here during seated training with video feedback

Arrows denote motion of vertical gates that serve as targets for the anklebot-controlled cursor. The knee brace is mounted to a fixed plate that supports the anklebot and restricts knee and hip motions, effectively isolating the ankle to move freely in either plantarflexion–dorsiflexion or inversion–eversion planes. The heel maintains contact with the base to provide a pivot for the foot.

Figure 2. Example of trajectory changes on 10 repetitions of a standard unassisted plantarflexion and dorsiflexion ankle targeting tasks before and after 6 weeks of performance-based ankle robot training

Note the improved consistency of responses, increased velocity (steeper slope), and smoother trajectories.