The goal of this study was to validate dynamic stability and forward progression determinants for the alternate foot placement selection algorithm. Participants were asked to walk on level ground and avoid stepping when present, on a virtual white planar obstacle. They had one step duration to select an alternate foot placement, with the task performed under two conditions: free (participants chose the alternate foot placement that was appropriate) and forced (a green arrow projected over the white planar obstacle cued the alternate foot placement). In order to validate the dynamic stability determinant, the distance between the extrapolated center of mass (COM) position, which incorporates the dynamics of the body, and the limits of the base of support was calculated in both AP and ML directions in the double support phase. In order to address the second determinant, COM deviation from straight ahead was measured between adaptive and subsequent steps. The results of this study showed that long and lateral choices were dominant in the free condition, and these adjustments did not compromise stability in both adaptive and subsequent steps compared to the short and medial adjustments, which were infrequent and adversely affected stability. Therefore, stability is critical when selecting an alternate foot placement in a cluttered terrain. In addition, changes in the plane of progression resulted in small deviations of COM from the end-point goal. Forward progression of COM was maintained even for foot placement changes in the frontal plane, validating this determinant as part of the selection algorithm.