Spring Mechanism Would Allow People To Run 50 Percent Faster With The Right Materials

Beating Usain Bolt in a fair contest may be an impossible dream for most people, but theoretically the right shoes could change that, if only we had the materials. Shahjehan/Sutterstock.com

Have you ever wanted to outrun the reigning Olympic Champion? Of course you have. Now scientists have shown it's theoretically possible for many of us, perhaps with modest training for couch potatoes, if we can enhance the materials from which we make springs.

The dream that springs could enhance our natural athleticism is an old one. Victorian England was terrorized with stories of “Spring-heeled Jack”, whose reported abilities to leap over 2.7-meter (9-foot) walls were attributed to some unknown device in his shoes. Not only that but advertising for sports-wear suggests that buying their products will give you an edge, with recent trials of one particular pair of running shoes leading some to question whether it should be allowed.

Vanderbilt University PhD student Amanda Sutrisno and supervisor Dr David Braun have much bigger dreams however, although it is unlikely anyone will allow their device into the Olympics. They propose a spring exoskeleton that would capture more of a runner's energy and catapult them on their way.

In some ways the idea is more like a bicycle or roller skates than a better pair of runners, reducing energy lost between the foot and the ground, but it would be less affected by an uneven surface.

By having a spring operate in parallel with legs, rather than in series, and programming the spring for optimum energy storage, the maximum speed of running could close much of the gap to bicycles. Amanda Sutrisno and David J. Braun/Vanderbilt University

The idea is, as yet, theoretical. Not only can you not buy one at a store, there isn't even a tested prototype. Nevertheless, Sutrisno and Braun have modeled the idea in sufficient detail to win publication in Science Advances. Their model allows for air-resistance and the loss of energy when the foot hits the ground.

Olympic runners using the springs would take longer to accelerate, the authors found, giving a substantial initial lead to someone of similar ability without the springs. Eventually, however, the springs allow their wearers to reach a speed 1.5 times as fast as those without them. A 100-meter champion would catch their counterpart at around the 68-meter mark and cruise on to an easy victory.

Catching the gold medal holder over 100 meters might be hard for ordinary mortals, even if given the springs advantage, but longer races might be a different matter. Since part of the spring's effect is to greatly extend the length of a stride, a little like running on the Moon, the long jump would probably just require staying upright to win.

Unfortunately, we are not yet ready to start manufacturing such devices. As part of their calculations, Sutrisno and Braun worked out the necessary stiffness and energy capacity for such springs. Existing carbon fiber is the closest, but still doesn't make the grade, so we will need a new generation of materials capable of storing more energy when compressed if the dream is to become a reality.

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