The study involved 12 professional badminton players (6 boys and 6 girls). The average age was 20.91 ± 2.03 years. All players were active participants in badminton competitions at the Russian level and had at least 5 years of experience in badminton competitions, the average time of badminton lessons for participants was 11.5 ± 3.7 years. All players reported that they had not had neuromuscular, vestibular, or visual system injuries for at least six months prior to their participation in the study and that they were generally in good physical condition. The study was conducted in accordance with the ethical principles of the Helsinki Declaration of Conducting Medical Research with the Participation of people as subjects of the study. The participants were informed about the testing progress and provided voluntary consent. The protocol of the study was approved by the Local Ethics Committee of Kazan Federal University (Protocol No. 34 of 27.01.2022).
In this study, the pedobarographic platform Tekscan HR (USA) was used to record data and measure plantar foot pressure and load distribution on the foot. The platform is a mat with 8448 sensors (sensors) on a surface area of 0.572 m by 0.457 m (0.261 m2). The thickness of the mat is 0.18 mm. The density is about 32 sensors per square centimeter. Each sensor operates on the principle of a piezoresistor. The raw data is read, converted into a digital signal of 256 points per frame (8 bits), and then transmitted to the VersaTek data logger (VWD-1), and then via USB 2.0 to a laboratory PC. The sensor platform was located on the floor. The HRF touch mat was calibrated for each participant taking into account his weight. Figure 1 shows an example of a two-dimensional (Fig. 1A) and three-dimensional (Fig. 1B) image of the distribution of plantar pressure.
The peaks in Fig. 1B reflect areas of high pressure, which means that large forces are acting in these areas during movement.
The results were analyzed using the program MatScan Clinical 6.62. (add-in "FootMat"). The footprint was divided into 12 anatomical segments (Fig. 2): the thumb (T1), the second finger (T2) and other toes (T3), the first metatarsal bone (M1), the second, third and fourth metatarsal bones (M2-5), the middle part of the foot (MF), medial part of the heel (MH) and side of the heel (LH). The peak pressure in kilopascals in each segment was estimated.
The data collection process consisted of five tests for each subject: calibration, standing in a European stand, loading in the form of 45 squats in 1 minute, standing in a European stand and performing a feed simulation. Each subject went through all five parts sequentially. Participants were given a 30-second rest between tests to minimize fatigue. All tests were conducted with the subject in socks.
European stand - heels together (the distance between the heels is 2 cm), socks are separated at an angle of 30 degrees. The subject stood straight, looked straight, without moving or talking. The values were recorded before and after the load in the form of 45 squats in 1 minute.
The "Submission" test. Participants were instructed to perform each test at a pre-determined starting point, and then return to the same point after completing the submission. We could divide the whole forehand into 3 phases: phase I, starting with a swing of the arm, the left leg in front, the center of gravity shifted back to the right leg, phase II, representing the movement of the racket stroke: an arc-shaped movement with the right shoulder moving forward and the body moving forward to the left leg, phase III, returning to the starting position. This action was characterized in detail by 6 stages, including the starting position (stage 1), support on the right leg, swing (stage 2), lifting the heel of the right foot from the ground (stage 3), impact moment, transfer of support to the left leg, lunge (stage 4), return of the right foot to the starting position (stage 5) and the return of the left leg to the starting position (stage 6). In this study, we presented data on the distribution of plantar pressure in the left leg stance phase at stage 2 (swing) and the left leg at stage 4 (lunge).
Descriptive statistics included the determination of the normality of the distribution of parameters, the calculation of the average and standard error of the average. The statistical significance of changes in plantar pressure parameters was evaluated by the nonparametric Wilcoxon criterion (the distribution differs from normal at the significance level) at the level of p < 0.05.