Though its muscles still have a vital role - after all, a quarter of the frog's entire mass is in its legs just for this purpose - these jumps would be physically impossible without its springy tendons.
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.
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