Meeting Abstract
Arboreal frogs navigate complex environments and face various changes in mechanical properties of the physical environment. Changes in substrate compliance and elasticity can pose challenges when jumping off structures like leaves or thin branches. An optimal, well-coordinated jump will allow the recovery of elastic energy stored in a springy substrate to amplify mechanical power by effectively adding an in-series spring to the hindlimbs. However, in a poorly coordinated jump the energy applied to the substrate is not recovered. The effective utilization of such springy substrates requires changes in the timing of muscle activation to allow energy recovery. We investigate the effects of substrate compliance on the hindlimb kinematics and motor control patterns during jumping in Cuban tree frogs (Osteopilus septentrionalis). We designed an actuated force platform, modulated with a real-time feedback BeagleBone controller to vary the stiffness of the substrate. We quantify the kinetics and kinematics of tree frogs jumping-off platforms at four different stiffness conditions. Additionally, we surgically implanted two EMGs in a knee extensor, the cruralis, and an ankle extensor, the plantaris, to examine the relationship between muscle activation patterns and substrate compliance during take-off. We find tree frogs do not modulate motor patterns or kinematics in response to substrate compliance. These results highlight a potential trade-off in amplified systems between jump performance and responsiveness in animals that rely on elastic mechanisms to amplify power. This work serves to broaden our understanding of how the utilization of elastic energy may alter the responsiveness of an organism to react to perturbations.
