ECSS Paris 2023: CP-AP10
INTRODUCTION: Spinning balls play a critical role in sports such as cricket, tennis, table tennis, and football. Among these, table tennis provides a distinctive testbed for studying ball aerodynamics, as drag and lift forces can exceed gravitational influence, producing pronounced drift during flight [1]. Spin also has a strong influence on post-impact behavior, significantly affecting bounce characteristics. Existing bounce models are typically tailored to specific interaction regimes and lack general applicability [2]. Understanding both flight and bounce mechanics requires precise measurement of position, velocity, and spin from experimental trajectories. Accurate kinematic extraction enables reliable trajectory prediction and provides key parameters immediately before and after impact, which are essential for analyzing bounce dynamics. METHODS: A high-speed stereo vision system was developed to capture the three-dimensional trajectories of sports balls, including the bounce phase. In this study, the system is applied to table tennis shots with pure topspin, backspin, sidespin, and their combinations. A custom computer vision pipeline processes synchronized footage from the two cameras to reconstruct the ball’s 3D position over time. Velocity vectors are computed at each timestep from the reconstructed positions. An inhouse mathematical framework is further implemented to estimate the instantaneous spin vector using information from either camera view. RESULTS: The position and spin extraction algorithms were validated against ground-truth references. The vision pipeline achieves sub-millimeter accuracy in reconstructing the ball’s position. Spin rate estimation errors were consistently below 5%. CONCLUSION: The developed pipeline provides a robust framework for extracting trajectory and spin parameters of spherical sports balls. The methodology is adaptable across multiple sports, and the resulting dataset of experimentally derived kinematics enables improved understanding and modeling of both aerodynamic behavior and bounce mechanics. [1] Clanet 2015 [2] Cross 2002
Read CV SAI VINEETH PASUNURUECSS Paris 2023: CP-AP10
INTRODUCTION: Several studies have examined countermovement jump (CMJ) force–time metrics over the course of a basketball match from the perspective of fatigue monitoring; however, no clear declines in these metrics have been demonstrated (e.g., Cabarkapa et al., 2024). This lack of decline may be attributed to inter-individual variability, because players in team sports assume different roles depending on positions. Therefore, it is necessary to clarify whether CMJ force–time metrics change over the course of a match and in relation to external loads in one-on-one sports, such as racket sports. The purpose of this study was to examine the relationships between external loads during a badminton match and CMJ force–time metrics. METHODS: Twenty-two collegiate badminton players participated in the study (age: 20 ± 1 years; height: 172.3 ± 5.5 cm, body mass: 64.4 ± 4.5 kg, Tier 3 [McKay et al., 2022]). They performed a badminton match while wearing an inertial measurement unit (IMU) on the lower back and all participants completed three games regardless of the outcomes of the first two games. Accumulated acceleration load (AAL) was calculated based on three-axis acceleration and further categorized by intensity into AALlow, AALmedium, AALhigh, and AALvery high. Three countermovement jumps without arm swing were assessed using a uniaxial force plate system at baseline (before the first game) and after the first, second, and third games. Relationships between each level of AAL intensity and relative changes in jump height, peak concentric force, and peak eccentric force during countermovement jumps were examined using Pearson’s correlation coefficient. RESULTS: CMJ height was higher after each game (means: 41.2–41.9 cm) than at baseline (37.5 ± 3.4 cm) (p < 0.05). Peak concentric and eccentric forces were also higher after each game (concentric means: 1411–1463 N; eccentric means: 1618–1653 N) than at baseline (concentric: 1389 ± 168 N; eccentric: 1539 ± 155 N) (p < 0.05). Relative changes in CMJ height from baseline to the third game were negatively correlated with AALvery high from the first to the third games (rs = −0.486, p < 0.05). Similarly, relative changes in peak concentric force were negatively correlated with AALhigh (rs = −0.496, p < 0.05) and AALvery high (rs = −0.599, p < 0.05), and relative changes in peak eccentric force was negatively correlated with AALvery high (rs = −0.473, p < 0.05). CONCLUSION: Although all participants performed a warm-up before the matches, badminton match play itself likely acted as an additional warm-up, as indicated by the increases in CMJ height and concentric and eccentric forces. However, the negative relationships between relative changes in external load and CMJ height suggest that players with a lower volume of high-intensity external load may gain greater benefit from this additional warm-up effect, whereas those with a higher volume may offset it.
Read CV Ryosuke AndoECSS Paris 2023: CP-AP10