Meeting Abstract

59.2  Friday, Jan. 6  Pre-landing muscle tuning in the forearm and shoulder of Bufo marinus MACESIC, L.J.*; GILLIS, G.B.; Mount Holyoke College, South Hadley, MA; Mount Holyoke College, South Hadley, MA lmacesic@mtholyoke.edu

In contrast to a typical frog, which often lands on its belly after a hop, the cane toad (Bufo marinus) is exemplary at landing. Toads use their forelimbs to balance the body for extended periods after impact as the hindlimbs are rocked back into contact with the ground. Recent investigations of antagonistic muscles acting at the elbow demonstrated that both the timing and intensity of pre-landing electromyographic (EMG) activity are tuned to hop distance. Longer hops lead to more intense pre-landing EMG activity, and in elbow extensors, the onset of activity occurs at a nearly fixed interval before landing, regardless of the length of the hop. In this study, we report results from antagonistic muscles acting at the wrist and shoulder joints to test whether pre-landing recruitment patterns of muscles acting more proximally and more distally to the elbow also change in response to hop distance. Data from wrist flexors (palmaris longus and flexor carpi ulnaris) show similar patterns of tuning with distance in both pre-landing activation timing and intensity. Likewise, antagonistic wrist extensors (extensor digitorum communis longus and palmaris carpi radialis) also exhibit tuned pre-landing activity patterns. Data from a suite of deltoideus muscles suggest that their role in bracing the forelimbs for landing may be minimal when compared to their role in positioning the forelimbs for landing during the aerial phase of the hop. This study demonstrates the importance of forearm muscles in stabilizing and controlling whole body movements of the toad during landing and provides a model system for understanding motor control strategies for controlled deceleration more generally.