Meeting Abstract

P1.154  Monday, Jan. 4  Pectoral and forelimb muscle activity during landing in Bufo marinus AKELLA, T; GILLIS, GB*; Mount Holyoke College; Mount Holyoke College ggillis@mtholyoke.edu

In toads, traversing a given distance is usually achieved by linking consecutive small hops together, which requires coordinated use of the forelimbs during each landing to rapidly decelerate the body and prepare the animal for the next hop. To better understand toad landing behavior we used high-speed video to characterize basic movements of hopping and implanted fine-wire electrodes into six muscles (two heads of the anconeus and pectoralis complexes as well as the deltoid and coracoradialis) to characterize their activity patterns in relation to locomotor kinematics. We divided hops into four phases. Takeoff phase one lasted from the onset of movement to when the forelimbs left the ground. Most muscles were quiescent in this interval except the anconeus, which occasionally exhibited small bursts associated with the onset of animal movement. Takeoff phase two was the time between when the forelimbs and hindlimbs left the ground. EMG activity typically began in all muscles during this phase. In the aerial phase, all but one of the muscles had their highest average EMG intensities. The exception was the long head of the anconeus, which was most intensely recruited in the landing phase, between forelimb and hindlimb touchdown during landing. All muscles are clearly important in resisting the impact forces when the forelimbs hit the ground, however, subtle differences in activity profiles suggest some degree of functional differentiation. For example, the coracoradialis and deltoid showed relatively high levels of recruitment in takeoff phase two implying a particularly important role in moving and positioning the forelimbs before landing whereas the long head of the anconeus had its highest recruitment after forelimb touchdown indicating a critical role in stabilizing the body during the landing phase.