Meeting Abstract

S5.3-4  Sunday, Jan. 5 15:00  What goes up must come down: how sloped surfaces impact the mechanics of locomotion BIRN-JEFFERY, AV*; HIGHAM, TE; University of California Riverside aleks.birnjeffery@ucr.edu

Terrestrial animals move over highly variable surfaces that include inclines and declines. Although the mechanical demands of inclined and declined locomotion differ greatly, and are both important for the animal, uphill locomotion is most commonly studied. An animal must overcome gravitational pull during uphill locomotion, requiring significant amounts of positive work. In contrast, downhill movement involves aspects of stability and resistance to gravity. However, both impart a toppling moment on the centre of mass (CoM) – be it backwards or forwards. On inclines animals tend to pull towards the ground with their forelimbs, but push away from the ground with their hindlimbs, indicating differential leg function. This reduces the pitching moment and also brings their CoM closer to the surface. Arboreal and rock-dwelling animals regularly go up and down inclines, making them well suited for studies of incline and decline locomotion. Geckos often occupy arboreal or rocky habitats, and those that do often possess an adhesive system that enhances movement on sloped surfaces. Using a generalist gecko, we examine how 3D forelimb and hindlimb kinematics, as well as the use of the adhesive system, differ between uphill and downhill locomotion. Comparable to previous studies, they moved significantly slower on inclines and exhibited a reduced shoulder height. Hindlimb stance and swing times were shorter on the decline condition, suggestive of a smaller contribution to propelling the CoM forwards. Understanding the mechanical demands of moving on a variety of slopes is critical given that animals that go up an incline will also need to come back down. Given the functional differences, there is likely a trade-off in functional demands between inclined and declined locomotion. Supported by NSF IOS-1147043.