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
INTRODUCTION: Elite table tennis (TT) performance requires a high level of explosive power and stroke speed. This study examined the relationships among explosive power indicators of the TT forehand drive and compared performance characteristics between players of different competitive levels using precision measurement technology. METHODS: Seven male national-level and five male regional-level TT players participated. All players completed two forehand drive protocols using an intelligent TT racket (Sheu & Wu, 2021): (1) 27 cross-court forehand strokes from a fixed position and (2) 27 cross-court forehand strokes with two-point lateral movement. Ball speed was obtained from high-speed camera recordings. Group differences in explosive power indicators were analyzed using the Mann–Whitney U test, while relationships among indicators were examined using Pearson’s product–moment correlation coefficients. Performance stability was assessed through trend analysis by averaging every five consecutive strokes. RESULTS: National-level players demonstrated significantly greater forehand drive explosive power performance than regional-level players. Significant correlations were observed among key explosive power indicators—swing efficiency, swing speed, and ball speed—across all participants, with consistent interrelationships also evident within each competitive group. Trend analysis revealed that national-level players exhibited greater performance stability across repeated strokes, whereas regional-level players showed increased variability, particularly during lateral movement conditions. CONCLUSION: Swing efficiency, swing speed, and ball speed function as integrative and interrelated indicators of TT forehand drive performance when assessed using intelligent racket technology. Higher-level players maintained more stable performance patterns and indicator relationships across different hitting conditions, while lower-level players exhibited reduced consistency under increased movement demands. These findings support the use of a multidimensional, technology-based approach for evaluating TT forehand drive performance. Future research should include larger samples, additional competitive levels, and female players.
Read CV Sheng Kuang WuECSS Paris 2023: CP-AP10