Meeting Abstract

P2.39  Sunday, Jan. 5 15:30  Indirect evidence of elastic energy storage and release during limb recovery in toad hopping GALLARDO, M*; SCHNYER, A; SCHIKOWSKI, E; COX, S; GILLIS, G; Mount Holyoke College; Mount Holyoke College; Mount Holyoke College; Univ. of Massachusetts, Amherst; Mount Holyoke College ggillis@mtholyoke.edu

Elastic energy is critical for amplifying muscle power during the propulsive phase of anuran jumping. In this study we use cane toads (Bufo marinus) to address whether elastic recoil is also involved after takeoff as the hindlimbs flex prior to landing. The potential for such spring-like behavior stems from the unusually flexed configuration of a toad’s hindlimbs in a relaxed state (mean knee angle = 109°). If during the takeoff phase the knee extends beyond this, underlying elastic tissues will be stretched, allowing passive recoil to help drive limb flexion during the aerial phase. To test if this happens we used high-speed video and electromyography to record hindlimb kinematics and electrical activity in a limb extensor (m. semimembranosus) and flexor (m. iliofibularis). Results show that longer hops involve greater degrees of knee extension during takeoff, and hops longer than 27 cm achieve knee angles greater than 109° (with the longest hops leading to values closer to 150°). Longer hops are also associated with significantly more intense semimembranosus activity and higher knee extension velocities during takeoff. Knee flexion velocities (after takeoff) also tend to increase with hop distance, but iliofibularis intensity decreases significantly. Thus, more knee extension during takeoff is associated with greater subsequent knee flexion velocities despite reductions in knee flexor intensity, a result consistent with elastic energy playing a role in knee flexion in longer hops.