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Toad Muscle Research (Image 2)

July 8, 2010
Toad Muscle Research (Image 2) Northern Arizona University postdoctoral research associates Ted Uyeno and Jenna Monroy prepare to feed a cricket to a cane toad as cameraman Ross MacIntosh from Discovery Channel Canada shoots the scene for a segment of the Daily Planet that is scheduled to air in the fall. [See related image Here.] More about this Image Scientists have long-held the theory that muscles behave largely like motors. But, Nishikawa suggests that muscle acts more like a spring. "Existing theories don't explain how muscles shorten rapidly," Nishikawa said. "Muscles can only shorten to do work; they can't do work by lengthening." For example, the jaw muscles in toads and chameleons shorten in the lower jaw, and the opening of the jaws causes the tongue to stretch by its own momentum. A toad's jaw muscles can produce forces greater than 700 times the animal's weight. "The best electric motor achieves about one-third of that force-to-weight ratio," Nishikawa noted. "When a toad or chameleon captures prey with its tongue, it exerts force over a distance. Figuring out how they do it has immense application to any device that actually moves." Nishikawa is working with Tom Sugar and his colleagues of Arizona State University's (ASU) Human Machine Integration Laboratory. Sugar and his team are building "SPARKy" (Spring Ankle with Regenerative Kinetics), a robotic tendon that mimics biology by storing and releasing energy during the ankle gait cycle. "Energy is stored as the leg and body rolls over the ankle, and then this energy is released in a powerful burst to propel the user forward. By mimicking biology, we are able to build a very lightweight and functional device," Sugar said. Findings from this research could lead to the design of more efficient electric motors, better prostheses and new medical treatments for neuromuscular diseases like Parkinson's. Nishikawa's studies of the neuromuscular basis for extremely rapid movements in animals, such as the toad snaring prey with its tongue, could leapfrog to a new model of muscle function, changing the standard representation of muscle as a motor. Nishikawa's and Sugar's research caught the interest of Discovery Channel Canada, which spent a day at NAU and a day at ASU taping for a segment of its Daily Planet show that will air in the fall. [Research supported by National Science Foundation grant IBN 02-40349, IOS 06-23791 and IOS 07-32949.] (Date of Image: May 2008)


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