A model for selecting alternate foot placement during human locomotion

The selection of alternate foot placement is based on visual inputs and the prediction of future foot placement combined with a set of internal rules that are guided by three determinants: minimum foot displacement, stability, and maintenance of forward progression. These three determinants are weighted differently, depending on different constraints. The first purpose of this review is to define and provide evidence to support this model. Alternate foot placement response latency appears to vary according to methodological and/or task constraints. The paradigms and latency measurement methods that are used to investigate alternate foot placement may have important implications for alternate foot placement control. Very short latencies to initiate alternate foot placement can be observed when walking on a treadmill, and longer latencies can be observed when walking on the ground. The second purpose of this review is to discuss differences in the latency to initiate alternate foot placement. The data reviewed herein indicate that looking at multiple parameters is important when studying movement selection and planning during human locomotion. Different latencies to select and implement alternate foot placement are part of a continuum that ranges from the most to the least automatic response.