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For 25 years, inventor Keahi Seymour has dreamed of running with the speed and loping gait of an animal. His inspiration struck at age 12, while he was watching a program about kangaroos. “The announcer said it moves at such an efficient gait by using its Achilles tendons as springs,” Seymour says. “I thought, ‘Why not replicate that in a device that could propel a human?’?” He began sketching footwear using ostriches, which, he discovered, run more like humans, as his model.

By the age of 17, he had built his first prototype using old Rollerblade boots, steel tubing, and bungee cords. Then, he built some 200 more. Today, Seymour’s Bionic Boot can propel him forward at 25 miles per hour. “You really feel superhuman,” he says. Eventually, Seymour hopes to boost the speed to 40 miles per hour, perhaps by enhancing the boots’ springy heels with electrical actuators. That, he expects, will take a few more prototypes.

The Bionic Boot’s Evolution


Bionic Boot 1998 Prototype

Bionic Boot 1998 Prototype

Seymour made his third prototype from wire mesh and fiberglass, powered by an “Achilles tendon” made from steel tubing and a bungee cord spring. These boots were raised 10 to 12 inches above the ground, the height that later proved the most stable. But they only reached 15 mph.


Bionic Boot 1998 Prototype

Bionic Boot 2010 Prototype

To reduce the weight of subsequent prototypes from 10 pounds to 6, Seymour swapped the fiberglass for aircraft-grade aluminum. He also replaced the springs, which had been made of thin rubber wound around a carabiner or a bolt, with thick rubber speargun tubing.


Bionic Boot 1998 Prototype

Bionic Boot 2012 Prototype

Seymour ditched the all-aluminum boot in favor of a housing molded from carbon fiber. To secure it to his legs, Seymour chose stable snowboard-boot clasps over lighter and flimsier Velcro fasteners. In later prototypes, he kept the carbon fiber but returned to Velcro, reinforcing it with nylon straps.

This article was originally published in the May 2015 issue of Popular Science, under the title “These Boots Were Made For Bounding.”