Stanford researchers have invented an ankle exoskeleton that increases walking speed by an average of 42%.
The challenge: For a healthy adult, 3 miles per hour is a comfortable walking speed (YMMV). Older people and those with neuromuscular diseases tend to walk more slowly, though, and that can negatively impact their quality of life.
Interventions such as strength training have been shown to increase walking speed by about 5%, but the Stanford team thought that an exoskeleton might be able to provide a more significant speed boost.
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Robotic assistance: Exoskeletons are wearable devices that assist or augment the user's movements — some help people lift heavy objects more easily, while others make it possible for people with paralysis to walk upright.
Stanford's ankle exoskeleton wraps around a person's calf and connects to a running shoe. A tether runs down the back of the device, and as a person walks, an external motor tugs on this tether. This lifts the wearer's heel upward as they push off the ground, providing a boost to help them walk.
The algorithm: Stanford developed an algorithm to control the timing of this tugging, ensuring it happened in a pattern that would increase a person's self-selected walking speed (that's the speed they choose to walk, so the device isn't forcing them to walk faster).
To train the system, 10 young, healthy adults walked on a treadmill that automatically adapted to their desired speed for about 2 hours. The algorithm made about 150 adjustments to the exoskeleton's torque for each person.
Participants walked an average of 42% faster while wearing the speed-optimized ankle exoskeleton than they did while walking in their regular shoes.
"We were hoping that we could increase walking speed with exoskeleton assistance, but we were really surprised to find such a large improvement," senior author Steve Collins said in a press release. "Forty percent is huge."
The cold water: This study proves that an ankle exoskeleton can significantly increase walking speed, but the device itself is still very much a prototype that can't be used outside the lab.
Additionally, it's only been tested on young, healthy adults so far — we don't know if older people or those with mobility issues would see the same 40% boost in walking speed.
"We were really surprised to find such a large improvement. Forty percent is huge."
The next steps: The researchers plan to continue developing the ankle exoskeleton prototype, with the goal of making it more comfortable.
They also want to conduct tests with older adults, and if the device works as well in that group, it wouldn't just bring seniors up to speed with young, healthy adults — it could make them faster.
"A 40% increase in speed is more than the difference between younger adults and older adults," Collins said. "So, it's possible that devices like this could not only restore but enhance self-selected walking speed for older individuals..."
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