Meeting Abstract

34.6  Tuesday, Jan. 5  Building a robotic link between muscle dynamics and hydrodynamics RICHARDS, Christopher/T; Harvard University richards@fas.harvard.edu

Physiologists have long appreciated that the temporal pattern of muscle force depends on the level of neural activation and the shortening velocity against a load. This well-established relationship has enabled modeling of interactions between muscle activation and muscle force that determine limb motion in terrestrial animals. Analogous principles governing muscle mechanics during swimming are less well known, in part, because of the difficulty of modeling forces against limbs moving in water. To address this problem, a frog-inspired robotic platform was built to measure both muscle force and hydrodynamic force required to translate and rotate a rigid model frog foot in water. A software-controlled servo drives fore-aft foot translation while a frog plantaris muscle, isolated from Xenopus laevis , powers foot rotation. The robotic foot will reach a peak translational velocity of ~0.8 to 1.0 m/s, which is within the range observed in frogs swimming at moderate speed. Varying the timing and magnitude of foot translation as well as varying muscle activation parameters (timing, magnitude and waveform pattern) will determine how hydrodynamic forces (due to both foot translation and rotation) influence the muscle work and power required for effective propulsion. Additionally, custom force transducers will measure hydrodynamic forces on the foot. Using this rig, I aim to bridge the understanding between neural input and muscle mechanical output by analyzing the time course of muscle force and velocity in response to observed hydrodynamics.