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Surprising Science

Springy Ankle Device Improves Walking Efficiency 7%

Biomechanical scientists have created a simple device that can increase walking efficiency, or "human gas mileage," by an average of 7 percent when worn around the ankle. 

Biomechanical scientists have created a simple device that can increase walking efficiency, or “human gas mileage,” by an average of 7 percent when worn around the ankle. Weighing about a pound, or the typical weight of a loafer, the device fits inside the shoe and works to coordinate the movements of the calf muscle and Achilles tendon. 

Researchers at Carnegie Mellon University and North Carolina State University who created the device found through biometrical analysis that (1) the ankle is the primary source of power in human walking and running and (2) that the Achilles tendon is not itself a source of power, but functions more like a clutch.

By providing a more advanced clutch than what human biology offers, the device improves walking efficiency by up to 12 percent for more advanced users, and the average boost in efficiency is equivalent to removing a 10-pound backpack from the person walking or running.

Dr. Gregory Sawicki, a biomedical engineer who worked on the project, explains how the device functions:

“The unpowered exoskeleton is like a catapult. It has a spring that mimics the action of your Achilles’ tendon, and works in parallel with your calf muscles to reduce the load placed upon them. The clutch is essential to engage the spring only while the foot is on the ground, allowing it to store and then release elastic energy. Later it automatically disengages to allow free motion while the foot is in the air.”

While larger exoskeleton devices have required external power sources like batteries to operate, the new device works with a simple spring, allowing greater distances to be covered by exerting the same amount of energy, or saving energy over the same amount of distance. 

Researchers say that the device could be extremely useful in helping the aged to walk and individuals who typically carry heavy loads such as delivery workers and soldiers. What is surprising about the simple mechanics of the device is how easily it improves on millions of years of selective evolution. Indeed, engineers typically look to copy nature when making efficient devices. 

So why did nature stop at “good enough” when it came to human locomotion? For some additional insight in the matter, Richard Dawkins explains how evolution selects for survival, likening our bodies to gene machines. During his Big Think interview, Dawkins contradicts the maxim that whatever doesn’t kill you makes you stronger. In the case of evolution, what doesn’t kill you may just stay the same. 

“We’re gene machines in the sense that a body is constructed by genes that have been successful in surviving in the past; they’re good at surviving because they’re good at constructing machines in which they survive. So a body is a machine for the propagation of the genes that built it.”

Read more at Science Daily.


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