## 2 Materials and Methods
### Procedures  
The pressure platform was located in the center of a corridor that was 6.4 m long and was flush with the floor surface. Subjects performed the first, second, and third steps barefoot [15; 23]. Subjects were instructed not to look at the platform or the ground to protect the reliability of the measures [23]. We randomly assigned the order of the steps (first, second, and third) [16; 26; 27; 28; 29; 30] and the lower limb (left vs. right) to be assessed. Four or five tests were performed on each protocol to familiarize the subject with the procedure and to determine his or her starting position. These tests ensured a successful arrival of the full foot on the platform. A comfortable walking speed was chosen by the subjects [22; 30; 31]. After reaching the platform, the subjects continued to take a minimum of 3 to 4 steps [30]. We excluded trials in which the subject's entire foot did not make contact with the platform [8]. We recorded measurements in five successful trials per leg and step combination (30 trials in all per subject in a session).  
We repeated the same data collection procedures in a second session at the same hour of the day one week after the first session, with the objective of checking the reliability of the data collected in both weeks and demonstrating that the test is reproducible. We made a new randomization of steps and limbs for this session. Subjects wore the same shoes on session days (although they participated barefoot).  
The platform was made with capacitive sensors. The dielectric material of which they consisted has excellent elastic properties so can return to the original position after use. After each trial, we waited 30 s to allow the platform material to return to its original state [31]. The Podoprint (Medicapteurs; Balma, France) platform we used has an active area of 400 mm \(\times\) 400 mm, with 2304 sensors [31].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Total Group** & **Female Group** & **Male Group** & \\  & **n = 19 (100\%)** & **n = 59 (49.6\%)** & **n = 60 (50.4\%)** & **\(p\)-Value \({}^{*}\)** \\  & **Mean (SD)** & **Mean (SD)** & **Mean (SD)** & \\ \hline Age (years) & 30.50 (3.65) & 29.76 (5.15) & 31.22 (6.06) & \(p\) = 0.161 \\ Weight (kg) & 67.28 (11.92) & 58.74 (6.66) & 75.67 (9.81) & \(p\) = 0.001 \\ Height (cm) & 170.43 (8.94) & 163.65 (5.58) & 177.10 (6.16) & \(p\) = 0.001 \\ Shoe size (Eu) & 40.67 (2.68) & 38.46 (1.21) & 42.85 (1.78) & \(p\) = 0.001 \\ \hline \hline \end{tabular} Abbreviations: kg, kilograms; cm, centimeters; BMI, body mass index; SD, standard deviation; CI 95%, confidence interval 95%. In all the analyses, \(p\) < 0.05 (with a 95% confidence interval) was considered statistically significant. \(p\)-values are from a Student’s \(t\)-test \({}^{*}\).  
\end{table}
Table 1: Clinical characteristics of the sample population.  
Technical specifications of the pressure platform are shown in the Table 2. This pressure platform is indicated for use in studies of footprints during the stance phase of the gait cycle [21; 32; 33]. We used the platform in self-calibrating mode. We used the manufacturer's software to analyze the data.