(A). Stance traces. Representative plot of an animal walking at 28.82 mm/s. Traces are generated by the position of the stance phase footprints relative to the body center (set at 0.0,0.0). For each leg, stance onset corresponds to the Anterior Extreme Position (AEP) while stance offset is termed Posterior Extreme Position (PEP). (B). Method to quantify the stance linearity index. For each stance trace (brown), a smoothed trace is generated (using data from every five frames; yellow trace), and the average of the difference between these two lines (orange arrows) corresponds to the stance linearity index. (C). Stance linearity as a function of speed. Each data point corresponds to the average of all traces for all six legs for a single video greater than ∼34 mm/s, stance linearity becomes constant (red box). (D). Method to quantify footprint clustering. For each set of AEP/PEP footprints (red circles), an average ±STD xy point is created (blue cross). The footprint clustering value is calculated as the vector sum of the two STD values (orange arrow). (E). Quantification of footprint clustering. Data were grouped into slow (<20 mm/s), medium (between 20 and 34 mm/s) and fast (>34 mm/s) speeds. Boxplots represent the median as the middle line, with the lower and upper edges of the boxes representing the 25% and 75% quartiles, respectively; the whiskers represent the range of the full data set. Values are normalized for body size. Asterisks indicate the significance of the decrease in footprint clustering between the AEP and the PEP (using the paired parametric t test in the case of the slow speed group and the Wilcoxon non-parametric test for the remaining groups, **p<0.005, ***p<0.001). A comparison between the three speed groups also displays statistical significance (Kruskal–Wallis-ANOVA, p values of 0.0015 and 0.0014 for AEP and PEP, respectively). Dunn's post hoc significance tests show: slow AEP vs medium AEP, not significant (NS); medium AEP vs fast AEP, **; slow AEP vs fast AEP, **; slow PEP vs medium PEP, NS; medium PEP vs fast PEP, NS; slow PEP vs fast PEP, ***. (F). Footprint position relative to the body center. Data were pooled as in the previous panel. AEP and PEP values for each leg are represented on the left and right sections of the plot, respectively. Values are normalized for body size.