Meeting Abstract
43.4 Saturday, Jan. 5 Turning Mechanics in Running Goats MORENO, C.A.**; BIEWENER, A.A.; Harvard University; Harvard University cmoreno@oeb.harvard.edu
Terrestrial animals frequently must execute vigorous running turns, especially during predator-prey interactions. Though this behavior is critical for survival and places extreme demands on the musculoskeletal system, the mechanics of turning are not well understood. Despite recent work in a variety of taxa, a rigorous analysis of the mechanics of turning in cursorial quadrupeds has yet to be published. Our goal was to describe the precise mechanisms by which upright, cursorial quadrupeds use their limbs to initiate and execute running turns. We hypothesized that upright quadrupeds would use their forelimbs for braking and medial impulse while the hindlimbs would be used mainly to accelerate in the new heading. We collected 3-D ground reaction force (GRF) data and kinematics from goats performing 90° turns on an indoor track at a range of speeds. We analyzed moments about the estimated COM and compared centripetal forces with the GRFs generated during a given gait. We also calculated roll/adduction angles at the shoulder and pelvic girdles to account for the slight decoupling of these regions. We found that in all turns, the forelimbs and hindlimbs both generate medially directed impulses, and the shoulder girdle leads the pelvic girdle in both yaw and roll components. In trotting, the inside and outside limbs produce similar impulses, whereas in galloping the outside limb produces significantly greater impulses. Lateral flexion and rotation may be produced via the trunk musculature to reposition each limb girdle for the next contact. We are developing a geometric model to relate the roll angle of the body with the medial GRF necessary to counter the toppling moment produced during turns. Despite the inherent experimental challenges involved with studying non-steady behaviors, they are imporant for assessing locomotor performance in terrestrial animals.
