Reducing the metabolic energy of walking and running using an unpowered hip exoskeleton.
Tiancheng Zhou, Caihua Xiong, Juanjuan Zhang and 3 others
PMID 34092259WHAT IT FOUND
An unpowered hip exoskeleton reduced the metabolic cost of both walking and running in healthy young men.
Walking energy use dropped by 8.2% and running by 9.1% at their respective optimal spring stiffnesses, or by roughly 7% for both at a single common setting.
Key findings
01With optimal spring stiffness for each gait, the exoskeleton reduced the metabolic rate of walking by 8.2% ± 1.5% and running by 9.1% ± 1.3%.
02Using a single common spring stiffness, metabolic rates were reduced by 7.2% ± 1.2% for walking and 6.8% ± 1.0% for running.
03The reduction in metabolic cost was associated with decreased activity in the rectus femoris, a major hip flexor, in both gaits.
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 nine healthy young men, so results may not apply to older adults, those with gait pathologies, or other genders. The exoskeleton cannot autonomously switch between walking and running or adjust to standing, limiting its practicality for daily life. The optimal spring stiffness for walking changes with speed, and the current design does not adapt to this. The precise biomechanical mechanisms for the metabolic reduction are inferred from muscle activity rather than directly measured tendon dynamics. The study did not provide individualized assistance, which previous work suggests could yield greater benefits.
Declared interests
The authors declared no competing interests. The study was supported by non-U.S. government funding.
The easy way to misread this
Do not assume this exoskeleton will reduce metabolic cost for patients with gait abnormalities or older adults. The study was conducted on nine healthy young men, and the authors note that optimal assistance likely varies by age and individual biomechanics.