Characterizing the relationship between peak assistance torque and metabolic cost reduction during running with ankle exoskeletons.
Delaney E Miller, Guan Rong Tan, Emily M Farina and 2 others
PMID 35549977WHAT IT FOUND
Tethered ankle exoskeletons reduced running energy cost by 24.8% at high torque in three runners.
Benefits plateaued at higher assistance levels. Generic late-timing assistance matched optimized settings, suggesting portable devices need high torque but not individual calibration.
Key findings
01Running energy cost decreased as exoskeleton assistance torque increased, reaching a 24.8% reduction at the highest tested level.
02The relationship between assistance torque and energy savings followed a decaying exponential curve, indicating diminishing returns at higher torque levels.
03Optimized assistance timing was consistent across participants, suggesting generic late-timing settings could provide near-optimal benefits without individual calibration.
STILL TO COME
How it was doneWhat they found
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What it does not show
Only three participants were studied, limiting generalizability. All participants were experienced runners with high fitness levels, so results may not apply to novice or clinical populations. The study used tethered exoskeletons with off-board motors; portable devices will carry added mass that could offset metabolic benefits. Peak torque was limited to 0.8 Nm/kg due to user discomfort and stability concerns, so the true maximum benefit is unknown.
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 these metabolic reductions apply to portable, wearable exoskeletons. The study used tethered devices with off-board motors, eliminating the weight penalty that portable units will introduce.