59.4 Friday, Jan. 6 Extrinsic loading in Cuban tree frog jumping ABBOTT, EM*; AZIZI, M; ROBERTS, TJ; Univ. of California, Irvine; Univ. of California, Irvine; Brown University firstname.lastname@example.org
It is common for locomoting animals to bear additional loads. It may occur naturally, as with gravidity or large feeding events, or artificially, such as with any weight lifting activity. Jumping with external loads has been studied in humans to determine maximal performance, develop efficient training programs and define muscular properties. However, loading effects in animals specialized for saltatory locomotion have not been thoroughly studied. We examined the force-load relationship of Cuban tree frog (Osteopilus septentrionalis) jumping to assess whether the mechanics of extrinsically loaded jumping are indicative of either a muscular or an elastic spring model. It was assumed that in jumps powered solely by muscle, the forces produced during a jump would increase with increased extrinsic load (F=ma). On the other hand, in jumps utilizing an elastic mechanism, forces produced during jumping would not increase with extrinsic load and would be a function of the constant elastic properties of the spring (F=kx=ma). Five individuals (body mass 15.1-32.2g) were jumped from a force plate to quantify peak power, work, peak force, takeoff velocity and jump duration. The frogs were loaded with removable custom made nylon backpacks placed near the center of mass and filled with measured amounts of lead shot. Each individual was jumped with six different external loads equivalent to 0%, 30%, 60%, 90%, 120% and 150% of body weight. We found that these frogs maintain consistent work and peak force performance across all loads. Therefore, we conclude that even under substantial loading conditions, Cuban tree frogs are utilizing elastic mechanisms during their jumps. Supported by NSF grant 642428 to TJR.