Meeting Abstract

86.4  Tuesday, Jan. 6  Fitting the closed-loop dynamics of human running on a split-belt treadmill LEE, J.*; CHOI, J.T.; BASTIAN, A.J.; COWAN, N.J.; Johns Hopkins University; Johns Hopkins University; Johns Hopkins University; Johns Hopkins University jsl@jhu.edu

Healthy humans alter their gait when walking or running on a split-belt treadmill (i.e. a treadmill that allows independent speed control for each leg). When one leg is driven to move faster than the other, people immediately use feedback to change stance and swing times to maintain a 1:1 antiphase gait pattern. If the perturbation is sustained, they also slowly adapt feedforward control of their gait to further optimize spatial and temporal patterns. Here we present the first empirically fitted closed-loop dynamical model of steady running (i.e. no adaptation) on a split-belt treadmill. We captured body kinematics from a healthy human subject running on a treadmill under various belt-speed perturbations. A linear discrete-time model parsimoniously captures the evolution of the subject’s state, namely, forward body position, body height, and forward speed, at apexes. The model determines the next apex state by a linear combination of the current and previous apex states as well as the current and previous treadmill inputs. For our next step, we will fit our proposed model to perturbation trials in which subjects are adapting to a sustained split-belt condition. With proper detrending of the data as well as accounting for nonlinearities, we will test whether or not adaptation contributes to the overall closed-loop dynamics on the split-belt. If not, it would imply that feedback gains are not adapted, and that the adaptation can be attributed to modifications of the feedforward pattern alone.