Development of VariLeg, an exoskeleton with variable stiffness actuation: first results and user evaluation from the CYBATHLON 2016.
Stefan O Schrade, Katrin Dätwyler, Marius Stücheli and 5 others
PMID 29534730WHAT IT FOUND
Two users with complete spinal cord injury trained four months in a new walking exoskeleton.
They learned sit-to-stand, slalom, and tilted ground, but completed only 3 of 6 competition tasks. This is prototype evaluation, not proof of daily-use benefit.
Key findings
01Two users with spinal cord injury completed 43 and 52 sixty-minute training sessions; no falls occurred, but staff prevented three falls.
02At the CYBATHLON, the user completed 3 of 6 obstacles, placing 5th; stairs, ramp, and flat stones were not attempted because training time was insufficient.
03The variable stiffness knee actuator was not used to modulate stiffness during walking; training and competition used a fixed stiffness setting.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only two users were tested, so the results describe what happened to them, not how a typical group would respond. Skill ratings were subjective, not based on clinical assessments, and no fixed protocol was followed. The variable-stiffness actuator was not used to modulate knee stiffness during walking; training and competition used fixed stiffness. Stairs, ramps, and flat stones were not attempted at the CYBATHLON because there was not enough practice time. The device required crutches for balance and two supporting staff during new tasks. The prototype fits only users with height between 1.75 m and 1.90 m and weight up to 85 kg. Preparation time was substantial, with 30 min typical preparation and more than 80 additional hours for 95 sessions.
Declared interests
Funding is listed as ETH Research Grant ETH-22 13-2, ETH Foundation, and Swiss National Science Foundation National Center of Competence in Robotics.
The easy way to misread this
Do not conclude that variable knee stiffness improved walking or safety. The paper says the variable-stiffness actuator was not used to modulate stiffness during walking; training and competition used a fixed stiffness setting.