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Video: Catapulting Frogs

Credit: Current Biology, Henry Astley

On paper, a frog's leap is impossible. Research has shown that the amphibian's hop, which can launch one as far as it five times its body length, requires more power than its muscles can generate. Now a study of the northern leopard frog (Rana pipiens), chosen partly for its handy size and wide availability, reveals how the frogs make their prodigious jumps despite relatively small muscles: They turn themselves into catapults. With the help of high-speed x-ray videos, researchers found that the frog's calf muscle contracts well before its leap begins (see video; red line in graph indicates muscle activity). That indicates the muscle isn't directly powering the leap. Instead, researchers report online today in Biology Letters, the muscle loads elastic energy into the frog's ankle tendon, which then releases tension like a rope in a medieval catapult. The results indicate that the catapult method may be widespread among animals, the scientists say.

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