Temporal structure of variability reveals similar control mechanisms during lateral stepping and forward walking

Previous research exploring a lateral stepping gait utilized amount of variability (i.e. coefficient of variation) in the medial-lateral (ML) and anterior-posterior (AP) direction to propose that the central nervous system's active control over gait in any direction is dependent on the direction of progression. This study sought to further explore this notion through the study of the temporal structure of variability which is reflective of the neuromuscular system's organization of the movement over time. The largest Lyapunov exponent (LyE) of the reconstructed attractors for the foot's movement in the AP and ML was calculated. Results revealed that despite the obvious mechanical differences between a lateral stepping gait and typical forward walking, the central nervous system's organization of the movement of the feet is similar in the primary planes of progression, as well as the secondary planes of progression, despite being different anatomical planes during the locomotive tasks. In addition, consistent with previous studies exploring amount of variability, the secondary plane for both locomotive tasks proved to have larger LyE values than the primary plane of progression (F_1,9=35.086, p<0.001). This is consistent with less dependency from stride-to-stride in the secondary plane implying increased active control.