Frogs’ amazing leaps due to springy tendons

Frogs’ amazing leaps due to springy tendons

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A team of scientists say they have discovered a springy catapult tendon that allows frogs to leap far distances.

the key to frogs’ leaping lies in their stretchy tendons: Before jumping, the leg muscle shortens, loading energy into the tendon, which then recoils like a spring to propel the frog up, up and away. 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 tendon’s services. The study was conducted by Henry Astley and Thomas Roberts, both of Brown University, both of whom collaborated and recently published a paper on frog physiology in Biology Letters.

The pair of researchers at Brown University, filming frogs jumping at 500 frames per second with specially designed X-ray, show that the frog’s tendon stretches as it readies its leap and then recoils, much like a spring, when the frog jumps. The study is thought to be the first of its kind.

“Muscles alone couldn’t produce jumps that good,” Henry Astley, who studies the biomechanics of frog jumping, said in a statement released Wednesday.

As the frog readies itself to leap, its calf muscle shortens. After about 100 milliseconds, the calf muscle stops moving, and the energy has been fully loaded into the stretched tendon. At the moment the frog jumps, the tendon, which wraps around the ankle bone, releases its energy, much like a catapult or archer’s bow, causing a very rapid extension of the ankle joint that propels the frog forward. The entire jump — from preparation to leap — lasts about a fifth of a second, the experiments showed. Other frog species jump much faster.

“It’s the first time we’ve really gotten the inner workings, that we’ve put all the pieces (to frog jumping) together,” Astley said. “We now have a clearer idea what’s going on.”

“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 Roberts. “Other studies have presented evidence for an elastic mechanism, but Henry’s gives us the first glimpse of how it actually works.“

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