Figure 5.

Foot trajectories (A) and angular movement characteristics (B–D) during strides with different initial foot contacts. (A) Superimposed foot trajectories across all strides and all neonates (top), ensemble-averaged (mean ± SD) vertical foot displacements vs. normalized gait cycle (bottom), and the amplitude of vertical foot movements (mean ± SD). As the relative duration of stance varied across strides, a white region indicates an amount of variability in the stance phase duration. (B) Corresponding joint angular movements and their ROMs. (C) Ensemble-averaged foot, thigh and shank elevation angles and examples of 3-dimensional gait loops and interpolation planes on the bottom (4 steps for each condition). Gait loops are obtained by plotting the thigh waveform vs. the shank and foot waveforms (after mean values subtraction). The interpolation planes result from orthogonal planar regression. Percentage of total variation explained by 1st, 2nd, and 3rd principal components (PV₁, PV₂, and PV₃, respectively) is shown on the right. (D) Spherical spatial density of the u₃ vector directions for all steps. Each point corresponds to a single stride. Color scale indicates density diagrams calculated using the Kamb method for axial data with E = 2σ and exponential smoothing (see methods), the black contours outline the areas with density equal to E + 2σ. Asterisks denote significant differences between conditions.