# Gait Kinematics Analysis of Flatfoot Adults
## 2 Materials and Methods
### Assessment  
Foot posture was diagnosed based on clinical procedures including the Navicular Drop Test and the Resting Calcaneal Stance Position test, as those are clinically used by practitioners worldwide [29; 30; 31]. They were performed by a single physiotherapist with more than 6 years of experience in the use of these techniques. The same procedure was used for both groups. Before data collection, subjects were asked to maintain a weight-bearing barefoot stance position to perform both tests. First, the Navicular drop was evaluated using the Navicular Drop Test, where the mean of three measurement values define the drop severity. A rigid plastic-made ruler was placed by the practitioner perpendicularly to the ground that registers the distance between the ground and the navicular bone (millimetres). The talus was then inverted into a neutral position by the practitioner, and the procedure was repeated. The assessment of the differences in the positions quantifies the navicular drop severity [29]. Afterward, the angle between the rearfoot and the leg was assessed by the same practitioner using the Resting Calcaneal Stance Position test, where the mean of three measurement values define the angle. This angle was formed by the longitudinal bisecting line of the calcaneus and the longitudinal bisecting line of the distal third of the leg, which was drawn by the investigator in a prone \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Total** & **NF** & **FF** & **_p-Value** \\ \hline n & 31 & 16 & 15 & \\  & & (37.5\% Women) & (46.6\% Women) & \\ k & 62 & 32 & 30 & \\ NDT (mm) * & & 5.06 \(\pm\) 2.42 & 11.35 \(\pm\) 1.43 & 0.000 \\ RCSP (\({}^{\circ}\)) * & & 1.44 \(\pm\) 1.19 & 5.52 \(\pm\) 2.22 & 0.000 \\ Age (years) * & 23.26 \(\pm\) 4.43 & 21.69 \(\pm\) 2.98 & 24.93 \(\pm\) 5.17 & 0.045 \\ Height (m) * & 1.70 \(\pm\) 0.98 & 1.72 \(\pm\) 0.09 & 1.68 \(\pm\) 0.10 & 0.200 \\ Weight (kg) * & 75.14 \(\pm\) 14.94 & 75.92 \(\pm\) 17.03 & 74.32 \(\pm\) 12.90 & 0.772 \\ \hline \hline \end{tabular} n = sample; k = lower limb number; NF = Neutral Foot; FF = Flatfoot; * Mean \(\pm\) Standard Deviation.  
\end{table} 
Table 1: Groups characteristics. position. A rigid goniometer was used to measure this angle (Enraf-Nonius B.V, Rotterdam, The Netherlands) [31]. Following the aforementioned tests, three-dimensional computerized gait analysis was performed on both the FF and NF groups to assess movement characteristics such as joint angular kinematics and spatiotemporal gait parameters. Data were captured with a 10-camera Qualisys(r) 3D Motion Capture System (Qualisys AB, Gotebor, Sweden) with a predictive error of 25 mm and a maximum residual set at 6 mm. A full-body marker setup based on the IOR model [32] comprising fifty-three reflective kinematic markers was used on specific anatomical positions on the participants, namely on the thorax, the head, and the lower limbs. Tracking markers, i.e., four marker clusters, were placed over the thighs and shanks to improve segment tracking accuracy. Therefore, kinematic data were collected in a previously calibrated volume, with a calibration error bellow 0.7 mm and recorded at a 200 Hz sampling frequency. Before gait acquisition, subjects were asked to perform a bilateral stance posture assessment regarding model creation processing. Therefore, all subjects were instructed to walk barefoot at a self-selected and comfortable pace across an 8 -meter walkway, which allowed them to reproduce their daily gait. To standardize the gait initiation, a starting point was established so that participants could perform four gait cycles before reaching the force platforms to stabilize gait velocity. No other restrictions were placed on participants. At least fifteen passages were collected at a comfortable speed to generate sufficient data to obtain a mean value for each parameter being measured. There was a ten second rest period between trials.