Example Time Series of Stride Speeds (<i>S</i>_<i>n</i>) and Absolute Position (<i>P</i>_<i>n</i>).

<p>Data are shown for 240 consecutive strides from a typical trial for a typical human subject (HU) and for one typical trial each of each of the four model configurations (P_MIP, P_OVC, S_MIP, and S_OVC). All four model configurations yielded <i>S</i>_<i>n</i> time series that initially appeared qualitatively similar both to each other and also to humans (HU). Conversely, both of the Position Control models (P_MIP and P_OVC) qualitatively exhibited far less variance and far less “drift” in their absolute positions on the treadmill (<i>P</i>_<i>n</i>) than did humans (HU).