Meeting Abstract

P3.192  Sunday, Jan. 6  What goes up must come down: Forelimb kinematics in cane toads during jumping and landing KARAGIANNIS, EE*; MAYNARD, EM; VICKOWSKI, FB; MACESIC, LJ; GILLIS, GB; Mount Holyoke College; Mount Holyoke College; Mount Holyoke College; Wheaton College; Mount Holyoke College ggillis@mtholyoke.edu

Jumping anurans have long been a model for addressing questions in locomotor biomechanics. However, most research has focused on take-off, while landing remains less well explored. Cane toads (Bufo marinus) exhibit coordinated landing, using their forelimbs to decelerate and stabilize the body after impact. We’ve shown previously that forelimb muscle use in these animals is distance-dependent, with EMG signal timing and intensity varying predictably with hop distance. To better understand how these differences in muscle activity translate into forelimb movements, we studied elbow angle excursions during jumping and landing in six toads. We were interested in testing whether toads undergo similar amounts of elbow flexion after impact regardless of hop distance. We digitized joint landmarks and processed 3D coordinate data using custom Matlab routines to determine elbow angle excursions as well as rates of elbow extension and flexion before and after landing. During hopping, toads exhibited a consistent pattern of forelimb movements. First, as a hop started, the elbow extended (mean = 8°). After this initial extension the elbow flexed roughly 30° as the hands left the ground and were swung forward. In mid-air the toad re-extended the elbow prior to impact (mean = 41°). After impact, the elbow flexed 38° on average. Impact-related elbow flexion increased with hop distance, however, the amount of elbow extension that preceded impact also typically increased with distance. Thus, the final elbow angle reached after impact varied little, regardless of hop distance, suggesting that cane toads modulate mid-air elbow extension to compensate for impending impact-related flexion and prevent over-stretching of elbow extensors during landing.