BIKNEVICIUS, A.R.*; MULLINEAUX, D.R.; CLAYTON, H.M.; Ohio Univ.; Michigan State Univ.; Michigan State Univ.: Taking the walk for a run: Locomotor mechanics of lateral sequence singlefoot gaits.

The locomotor mechanics of lateral sequence singlefoot gaits were investigated. Icelandic horses using a walk and a t�lt, often described as a “running walk”, were ridden to record ground reaction forces (GRF) and limb kinematics. Icelandic horses smoothly transition from a walk to a t�lt, while faithfully remaining within the limb phase range characteristic of lateral sequence singlefoot gaits (15-35%). GRFs for fore and hind limbs for the t�lt were found to more closely resemble force profiles of running trots than walks. Individual limb GRFs were summed, to represent whole body GRFs, and integrated to obtain velocity and displacements of the center of mass for computation of kinetic and gravitation potential energies. All trials, including the fastest t�lt at 4.7 m/s, resulted in at least one limb maintaining ground contact throughout the stride. As the kinetic and gravitational potential energies cycled largely in-phase during the t�lt, the energy recovery by pendular mechanisms was limited. These findings reinforce the concept that aerial phases are not necessary for running mechanics. The results of this study provide insight into the mechanics of the other gaits and species, such as, the elephant which exclusively relies on lateral sequence single-footed runs for its fastest locomotion. (Supported by NSF 0080158 and McPhail endowment)