Meeting Abstract

6.2  Friday, Jan. 4  Where’s the catch? Examining the catch mechanism in anuran jumping using inverse dynamics. ASTLEY, H. C.*; ROBERTS, T. J.; Brown University henry_astley@brown.edu

Many animals use catapult mechanisms to produce extremely rapid movements for escape or prey capture, resulting in power outputs far beyond the limits of muscle. In these catapults, muscle contraction loads elastic structures, which then recoil to release the stored energy extremely rapidly. Many arthropods employ exoskeletal elements as a “catch mechanism” to lock the joint in place during the loading period, which can then be released to allow joint motion via elastic recoil. However, catapult mechanisms in vertebrates lack a clear anatomical catch. Several vertebrate catch mechanisms have been proposed, including a variable mechanical advantage at the ankle. In this mechanism, the muscle contracts at low mechanical advantage at first, which limits joint motion while the tendon stretches, followed by a transition to high mechanical advantage, which allows the tendon to recoil. To test this hypothesized catch mechanism, we collected simultaneous kinematics via XROMM and single-foot forces during the jumps of three Rana pipiens. We calculated joint mechanical advantage, torque, work, and power using inverse dynamics. Preliminary results show an increase in mechanical advantage at the ankle immediately prior to ankle extension, consistent with the variable mechanical advantage catch mechanism.