Researchers have developed exoskeleton boots that reduce the amount of energy expended while walking without the use of power aids, according to a report published in Nature. The technology could be a breakthrough in the rehabilitation of patients with stroke or neuromuscular disorders.
The boot uses a spring-and-ratchet mechanism that reduces the energy used while walking by 7% compared with walking in normal shoes.
Previously, experts were not sure that human locomotion could improve more than it already has after millions of years of evolution. Other devices that tried to make walking more energy efficient required an external power source or added too much weight to the legs, which offset any energy-preserving benefits.
People swing their leg forward when they walk, and elastic energy is stored mostly in the Achilles tendon of the opposite leg. When they push that foot into the ground and the heel lifts, the released energy propels the person forward.
To store this energy, the calf muscles have to “lock,” which actually expends most of the energy used in walking. The new exoskeleton has a mechanical clutch to help reduce this energy expenditure.
The exoskeleton is made of lightweight carbon-based materials. It has a spring that connects the back of the foot to just below the back of the knee, and the spring then connects to a mechanical clutch. Stretching the Achilles tendon engages the clutch while the spring stretches to store energy. When the other foot pushes down and releases energy, the clutch releases while absorbing the spring’s slack.
The researchers have been developing the exoskeleton for eight years, but were only just able to reduce the weight to <0.5 kg per leg. This light weight was crucial for providing an overall benefit in energy expenditure.
While some people have questioned why the researchers would want to reduce energy expenditure when so many adults are obese, the researchers believe the exoskeleton can benefit people who would otherwise find it hard or painful to move, especially stroke patients suffering from mobility problems.
They plan to test the boots on patients with various mobility issues, hopefully customizing the design to most effectively benefit different conditions.