Using high-speed X-ray photography, animal scientists at Brown University discovered frogs' tendons stretch as they ready their leaps and then recoil much like a spring.
"Muscles alone couldn't produce jumps that good," Henry Astley, who studies the biomechanics of frog jumping, said in a Brown release Wednesday.
Even though as much as a quarter of a frog's mass is in its legs, it would be physically incapable of jumping as far without the tendons' services, he said.
"In order to get truly exceptional jumping performance, you need some sort of elastic structure," Astley said.
As the frog readies itself to leap, he said, its calf muscles shorten and load energy into the stretched tendons.
At the moment the frog jumps, the tendons, which wrap around the ankle bones, release their energy, much like a catapult or archer's bow, causing a very rapid extension of the ankle joints that propel the frog forward.
"Frogs are interesting in their own right, but we are also confident that this study gives us insight into how muscles and tendons work together in animal movement," said biology Professor Thomas Roberts, who supervised Astley's work.