Frogs Amazing Leaping Ability Due to Springy Tendons
Posted on December 2, 2011
Frogs can leap several times farther than their physiology would seem to allow. Researchers at Brown University have discovered that the key to frogs' leaping lies in their stretchy tendons.
Before jumping, the frog's leg muscle shortens, loading energy into the tendon, which then recoils like a spring to propel the frog. Frogs have as much as a quarter of their body mass in their legs, but the researchers say frogs would be physically impossible of jumping as far without this stretchy tendon.
Henry Astley, who studies the biomechanics of frog jumping at Brown University, says, "Muscles alone couldn't produce jumps that good. In order to get truly exceptional jumping performance, you need some sort of elastic structure."
Astley and Thomas Roberts, associate professor of biology, examined jumps by the northern leopard frog (Rana pipiens), a pond frog common in the northeast United States. The researchers implanted metal beads into the shin bone, ankle bone and leg muscle of four frogs and then recorded their leaps with 3D X-ray video technology. The video footage was filmed at 500 frames per second. It displays the frog's jump about 17 times slower than normal. The video tracks the changes in the frog's leg muscle's length and joint movement before, during and after a jump.
As the frog prepares to jump, 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 (like a catapult or bow) causing a 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 researchers say other frog species are capable of jumping much faster than the northern leopard frog.
Take a look:
The research paper was published in the journal, Biology Letters. The National Science Foundation funded the research.
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