Optimized hip-knee-ankle exoskeleton assistance at a range of walking speeds.
Gwendolyn M Bryan, Patrick W Franks, Seungmoon Song and 5 others
PMID 34663372WHAT IT FOUND
For three expert users, a heavy exoskeleton cut energy cost by 26% at slow speeds and 50% at fast speeds.
Assistance did not lower cost below that of walking without the device when moving slowly.
Key findings
01Exoskeleton assistance reduced the metabolic cost of walking by 26% at slow speeds, 47% at medium speeds, and 50% at fast speeds compared to walking with the device turned off.
02Assistance did not reduce the metabolic cost of slow walking relative to walking with no device at all.
03Ankle plantarflexion torque was smallest for slow walking, while knee flexion torque remained similar across all speeds.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only three participants, all of whom were able-bodied expert users, so the results may not apply to patients with walking impairments or novice users. The exoskeleton emulator weighed 13.5 kg, which is much heavier than future commercial products might be, potentially masking benefits at slower speeds. The study was conducted on a treadmill, which does not replicate overground walking conditions. Torque was limited by participant comfort, meaning the device was not tested at its maximum potential assistance levels.
Declared interests
Funded by the U.S. Army Natick Soldier Research, Development and Engineering Center and the National Institutes of Health.
The easy way to misread this
Do not assume this exoskeleton will reduce the energy cost of walking for patients who walk slowly. At slow speeds, the assistance did not lower metabolic cost compared to walking without the device, likely because the weight of the 13.5 kg machine offset the benefits.