Search Results (79)

Resin-based carbon fiber composites exhibit outstanding comprehensive mechanical properties, including high specific strength, high modulus, corrosion resistance, low weight, stable dimensional performance and low thermal expansion coefficient, and they have been widely deployed in aerospace, wind power generation, automotive manufacturing, national defense equipment and sports equipment sectors. In aerospace engineering, these composites are employed to manufacture aircraft wings, fuselages and other key components, effectively reducing overall aircraft weight and enhancing fuel efficiency. For wind power facilities, large-scale turbine blades manufactured from such materials gain superior fatigue resistance and an extended service life. In automobile production, structural body parts made of these composites cut vehicle weight and improve energy utilization efficiency; in national defense equipment, they serve as lightweight protective components to boost shielding capacity, while high-performance rackets, bicycles and other sporting goods manufactured from the composites deliver better athletic performance and user comfort. Nevertheless, two critical drawbacks restrict their large-scale application in high-end manufacturing fields: insufficient interfacial bonding between carbon fibers and the resin matrix, and the inherent low ductility of cross-linked epoxy matrices. Therefore, strategies to regulate the mechanical performance of resin matrices and fiber–matrix interfaces have become a prominent research hotspot in recent years. This paper systematically reviews recent research advances regarding resin-based carbon fiber composite optimization, focusing on two mainstream technical routes: carbon fiber surface modification and resin matrix regulation. Meanwhile, prospective research directions are proposed, aiming to provide reliable theoretical references for the further development of this field. Full article

Background: While the biomechanical, physiological, and nutritional determinants of table tennis (TT) performance have already been summarized, a dedicated synthesis of players’ anthropometric and motor characteristics is still lacking. This review aimed to synthesize current evidence across different ages, genders, and competitive levels. Methods: BASE, PubMed, ScienceDirect, Scopus, Semantic Scholar, and Web of Science databases were searched for study selection. Cross-sectional studies investigating the anthropometric and motor characteristics of healthy TT players aged 7–40 years were considered eligible. Results: Thirty-one studies were included. Eighteen studies focused on motor characteristics, seven on anthropometric traits, and six examined both. Conclusions: Adult male TT players predominantly exhibit an endomorph–ectomorph profile with greater lean mass, whereas females show an endomorph–ectomorph somatotype. Moreover, higher-ranked athletes generally display greater lean mass. Compared to specific strength-based sports athletes, TT players tend to have lower limb circumferences and lower lean and muscle mass, while showing higher body fat than specific speed- and agility-based sports. Higher-level players tend to demonstrate faster reaction and movement times, as well as superior change-of-direction abilities. Compared to other racket sports, they tend to exhibit superior coincidence-anticipation timing under high stimulus velocities and distinctive motor coordination. In terms of strength, TT players show proficiency in horizontal jumps and dynamic back strength, despite lower vertical explosive power. The identified characteristics provide a descriptive profile of table tennis players and may inform future longitudinal research investigating their potential relevance for talent identification and development. Full article

Three-dimensional motion capture provides high-fidelity kinematic trajectories, but the extent to which different marker configurations retain discriminative information for tennis stroke recognition remains unclear. This study combined 3D motion capture with MiniRocket to compare seven upper-limb and racket marker configurations using data from 40 tennis-trained participants, 13 stroke types, and 10,133 valid movement samples. The configurations were the full-information group (ALL), full-arm group (AB), forearm group (FA), forearm + racket group (FR), upper-arm group (UA), racket group (RK), and watch group (WT). Model performance was evaluated using leave-one-subject-out cross-validation. All configurations achieved high performance in the three-class task. In the 13-class task, Macro-F1 was highest for ALL (78.76%), followed closely by FR (78.71%) and RK (78.28%). Holm-adjusted pairwise comparisons showed no significant differences among ALL, FR, and RK. FR significantly outperformed AB, FA, UA, and WT, whereas RK significantly outperformed FA, UA, and WT. Serve and overhead strokes were easiest to recognize, while several fine-grained baseline and net-play strokes showed lower F1-scores. These findings indicate that discriminative information is more strongly represented in the forearm-wrist-racket chain rather than simply increasing with marker count. Full article

The accumulation of discarded denim waste in landfills is causing environmental pollution, creating an urgent need for sustainable solutions. This study demonstrates the recycling of denim by extracting the indigo dye and fabricating the treated fabric into a composite to develop eco-friendly and high-performance materials. The waste denim was treated with sodium borohydride under controlled conditions without damaging the fibers. To utilize the denim waste, the decolorized fabric was shredded into fibers and incorporated into two polymer matrices i.e., ethylene vinyl acetate (EVA) and vinyl acetate, (VA) to fabricate a fiber-reinforced composite. The prepared recycled denim composites were compared with composites based on raw cotton fibers. The surface morphology of the composites was studied through optical microscopy and SEM analysis to examine the structural properties. Mechanical tests including tensile, charpy impact, flexural bending and drop-weight tests were performed to evaluate performance. The results showed that the raw composite had a higher impact strength of 11.5 kJ/m², while the recycled composite had 9.89 kJ/m², showing a slight reduction but maintaining good mechanical strength and lightweight properties suitable for applications such as table tennis rackets, a sustainable sports product, thereby supporting a closed-loop denim recycling approach within a circular economy framework. Full article

Identifying the impact location (“sweet spot”) on a tennis racket is crucial for performance evaluation in tennis training. However, existing approaches typically rely on expensive vision-based systems or specialized sensors, limiting their applicability in real-world scenarios. We propose a sound-sensor-based multi-task framework for racket impact localization using acoustic signals, combining radial region classification with continuous position regression. To effectively model complex acoustic patterns, we design a multi-expert convolutional neural network (CNN) architecture with multi-scale feature extraction and task-specific optimization. Each expert branch operates at a different temporal receptive field and is trained with tailored loss functions, enabling complementary learning of global patterns, class imbalance characteristics, and hard samples. The shared backbone jointly supports both classification and regression tasks, allowing the model to learn more informative and structured representations. Experimental results demonstrate that the proposed framework consistently outperforms conventional methods in radial region classification while achieving accurate impact position estimation. Furthermore, additive noise augmentation significantly improves robustness, enabling stable performance under noisy and practical sensing conditions. Full article

(1) Background: The aim of this study was to determine the biomechanical role of plantar pressure distribution in generating racket velocity during the topspin forehand in table tennis players, with particular emphasis on its relationship with stroke kinematics and performance level. (2) Methods: The study involved 14 male table tennis players divided into Elite and Sub-Elite athletes. Each participant performed a topspin forehand stroke. The study employed a biomechanical analysis combining inertial motion capture and plantar pressure measurement to assess the relationship between lower limb loading and racket velocity during the topspin forehand. (3) Results: The statistical evidence supports the subsequent phase-by-phase comparisons, indicating that the Elite (EL) and Sub-Elite players (SE) differ in execution of the topspin forehand, and the Elite group achieved significantly higher racket speed values in all phases (e.g., in hitting phase: SE-13.8 m/s, EL-15.6 m/s, p ≤ 0.001, d = 1.0; in post-impact follow-through phase: SE-13.8 m/s, El-16.1 m/s, ≤0.001, d = 1.3) and exhibited also a different pattern of foot loading. An analysis of the correlation between the plantar pressure and velocity of the racket in individual events revealed numerous significant correlations. (4) Conclusions: The study identified numerous correlations between the maximum plantar pressure and the maximum racket speed in the individual phases of the stroke. This demonstrates the active involvement of the feet throughout the entire kinematic chain of the topspin forehand stroke and highlights the importance of foot coordination for the outcome of this stroke, namely the speed of the racket-wielding arm. Full article

In padel, an emerging racket sport, evidence regarding competition demands in adolescent players remains limited. Therefore, this study aimed to analyze absolute external load during official competition in male and female U18 padel players. A total of 18 official matches from the Spanish Championship of Regional Teams were analyzed. Eighteen U18 players (9 females: age 15.1 ± 1.5 years, height 162.9 ± 8.2 cm, body mass 54.6 ± 9.1 kg; 9 males: age 15.4 ± 1.8 years, height 175.1 ± 9.4 cm, body mass 67.2 ± 11.0 kg), competing at the regional and national levels, were monitored using OLIVER™ inertial devices. External load variables included playing time, total distance, high-intensity accelerations and decelerations, changes of direction, time spent at high metabolic power, session volume, session intensity, and maximum speed. Statistical analysis was performed using linear mixed models to compare differences between sexes. Male players showed significantly higher values than female players in playing time (82.34 ± 23.95 vs. 51.03 ± 12.39 min; p < 0.001) and total distance (3958.50 ± 242.57 vs. 2225.54 ± 257.29 m; p < 0.001). They also presented significantly greater values in high-intensity external load variables, including accelerations, decelerations, changes of direction, time spent at high metabolic power, session volume, and session intensity (all p ≤ 0.009). No significant differences were found for maximum speed (p = 0.074). These findings suggest that official competition demands differ according to sex in U18 padel and may help inform more specific training prescriptions and load-monitoring strategies. Full article

A backhand flick is frequently used in table tennis to initiate offensive play, yet how racket motion evolves during subsequent stroke transitions remains insufficiently characterized. This study examined racket kinematics in two common follow-up combinations: a backhand flick followed by a backhand fast block (BFBB) and a backhand flick followed by a forehand fast block (BFFB). In a within-subject design, ten national-level male players performed both combinations, and racket motion was recorded using a three-dimensional motion capture system at 200 Hz. Racket velocity, phase duration, and spatial displacement were quantified across the stroke sequence, and within-player differences between the two stroke transition combinations following the backhand flick were examined. Compared with BFBB, BFFB showed higher racket velocity at most key moments, particularly near ball contact, whereas no significant difference was found at the end of the follow-through. Backward-phase duration did not differ between the two conditions, but BFFB showed longer durations during the hitting and follow-through phases, together with a longer overall duration. BFFB also exhibited greater directional displacement across multiple phases, whereas BFBB was characterized by a more compact spatiotemporal pattern. These findings provide biomechanical evidence that different follow-up strokes after an identical backhand flick are associated with distinct patterns of racket motion during stroke transitions and may offer a kinematic reference for sequence-specific training in table tennis. Full article

This study compared the kinematic and neuromuscular characteristics of the tennis forehand drive between high-performance (HP) and intermediate (INT) players. Eighteen right-handed male players (HP: n = 9; INT: n = 9) performed cross-court forehands while three-dimensional motion capture and surface electromyography (EMG) were recorded from the dominant upper limb and trunk. Kinematic and EMG data were time-normalized to the forward swing. One-dimensional statistical parametric mapping two-sample t-tests were used to compare joint angles, angular and linear velocities, and EMG amplitude waveforms between groups. Bonferroni-corrected significance levels were set at α = 0.0017 for kinematic variables and α = 0.0063 for EMG data. HP players exhibited greater racket linear velocity during the final part of the forward swing, accompanied by higher shoulder, elbow and wrist linear velocities, whereas hip linear velocity did not differ between groups. Joint angles were broadly similar, with SPM revealing only slightly greater early knee flexion in HP players. In contrast, HP players showed higher hip and knee angular velocities and greater wrist angular velocities in both flexion/extension and radial/ulnar deviation towards impact. EMG patterns were generally comparable, but HP players displayed higher biceps brachii activation in two significant clusters during the mid-to-late forward swing and greater triceps brachii activation in the late forward swing. No significant differences were observed for deltoid, pectoralis major, latissimus dorsi, flexor carpi radialis or extensor carpi radialis. These findings indicate that superior forehand performance in HP players is associated primarily with refined segmental coordination, greater lower-limb and distal segment velocities, and locally increased elbow muscle activation, rather than with widespread increases in upper-limb or trunk muscle activity. Full article

This study addresses the issue of inaccurate results in traditional table tennis player classification, which is often influenced by subjective judgment and environmental factors, by proposing a youth table tennis player classification system based on sensor fusion and the random forest algorithm. The system utilizes an embedded intelligent table tennis racket equipped with an ICM20948 nine-axis sensor and a wireless transmission module to capture real-time acceleration and angular velocity data during players’ strokes while synchronously employing a camera with OpenPose to extract joint angle variations. A total of 40 players’ stroke data were collected. Due to the limited sample size of top-tier players, the Synthetic Minority Over-sampling Technique (SMOTE) was applied, resulting in a final dataset of 360 records. Multiple key motion indicators were then computed and stored in a dedicated database. Experimental results showed that the proposed system, powered by the random forest algorithm, achieved a classification accuracy of 91.3% under conventional cross-validation, while subject-independent LOSO validation yielded a more conservative accuracy of 70.89%, making it a valuable reference for coaches and referees in conducting objective player classification. Future work will focus on expanding the dataset of domestic high-performance athletes and integrating precise sports science resources to further enhance the system’s performance and algorithmic models, thereby promoting the scientific selection of national team players and advancing the intelligent development of table tennis. Full article

This study explored the influence of game-specific on-court drills on external load in junior and professional male tennis players. Using wearable inertial technology, a total of 345 drills performed during a training microcycle were analyzed. Drills were classified according to the usual tennis game situations (i.e., serve, return, baseline, net play, and all-court), and load was quantified through distance covered, explosive distance, accelerations, decelerations, and Player Load. Significant differences were found in load across playing situations, with baseline and all-court drills producing the highest demands, especially in distance and Player Load. Serve drills consistently showed the lowest external load, while acceleration and deceleration values remained stable. Age group comparisons revealed that juniors covered more distance and experienced higher overall load in return and baseline situations, while professionals showed greater acceleration and deceleration values. These findings highlight the relevance of adapting training load to the specific demands of the game situations, the developmental stage, and the skill level of players. Coaches and sports scientists can use these insights to better plan, monitor, and individualize training programs for injury prevention and performance optimization in high-performance tennis. Full article

Objective: The aim of this study was to analyse the evolution of heart rate variability (HRV) during official competition in high-level amateur padel players according to match outcome. Methods: HRV was measured in 44 individual recordings obtained across 11 matches involving 12 padel players. Measurements were taken before the match (PRE), during three sets (S1, S2 and S3) and during the two rest periods between sets (R1 and R2). Time-domain variables analysed included mean R–R interval (Mean RR), standard deviation of normalised R–R intervals (SDNN), root mean square of successive differences (RMSSD), natural logarithm of RMSSD (LnRMSSD) and standard deviation of heart rate (STD HR), while nonlinear variables included the transverse (SD1) and longitudinal (SD2) axes of the Poincare plot, stress score (SS) and the sympathetic–parasympathetic ratio (SNS/PNS ratio). Results: Significant fluctuations in HRV were observed throughout the match. Players who won exhibited significantly higher values of Mean RR, SDNN, RMSSD, LnRMSSD, SD1 and SD2 during S1 (p < 0.05), and higher Mean RR, RMSSD, LnRMSSD and SD1 during R1 (p < 0.01). These differences diminished as the match progressed, disappearing in the later phases (S3, R2). Temporal analysis revealed that both groups showed parasympathetic recovery during the rest periods. Conclusions: This study provides novel evidence on the temporal dynamics of autonomic regulation in padel, showing that match outcome is associated with differences in cardiovascular regulation during the initial phases of competition. These findings support the usefulness of HRV monitoring for performance management in real competition settings. Full article

In padel, there exists four possible outcomes after hitting: into play, winners, forced errors and unforced errors. Courts are divided into three zones: baseline, transition and net. The objective of this study was to analyse how shot outcomes may vary based on the hitting location where they were executed. A total of 10,321 shots from the Premier Padel 2022 circuit were assessed through systematic observation. Type of shots, hitting locations and final outcomes were analysed. Significant differences (p < 0.001 to 0.005) were found in shot outcomes across hitting locations. At the baseline, into-play forehands, backhands, and lobs were performed more frequently than at the net (p < 0.001) and resulted more often in unforced errors compared to the transition zone (p = 0.003–0.026). Overhead shots were performed more frequently at the transition zone compared with the others, specifically in into play (p ≤ 0.001 to 0.026), winners (p = 0.008 to 0.026) and unforced errors (p = 0.005 to 0.038). The net was the only zone where all types of outcomes were observed, with volleys being the most frequently performed shot. These results confirm that shot outcomes vary significantly according to their hitting location. Full article

Pickleball is a recent sport, and very little scientific information exists on its match performance, especially for mixed doubles. Therefore, the aim of this study was to describe the performance profile in relation to sex differences in terms of shot outcome, margin of victory, and advantage. Seventeen elite mixed double matches from Professional Pickleball Association tours were analyzed, specifically considering the final as well as the penultimate shot with regard to the sex of the opponent who played it to analyze the inter-player dynamics between the opponents. Elite mixed pickleball matches have been characterized by 1:1.4 work-to-rest ratio, with rallies meanly lasting 10.6 s and separated by 11.4 s between them. Among the 1678 final shots analyzed, males played significantly fewer forced errors and more winners than females, especially when the penultimate shot was played by a female opponent. No sex differences emerged when the penultimate shot was played by a male opponent. Additionally, males played more winners both when leading and when winning the match. Mixed doubles pickleball matches appear to be partially influenced by sex-imbalanced game dynamics, with a higher number of winners played by males, particularly when the preceding shot is played by a female, suggesting that this format offers only moderate inclusivity between sexes. Full article

Background/Objectives: This study examined the effects of a six-week eccentric–reactive training program on neuromechanical markers of lateral explosiveness, asymmetry, and stretch-shortening cycle (SSC) efficiency in elite male youth table tennis players. Fourteen national-level athletes (mean age = 16.6 years) were assigned to either an experimental group (EG, n = 7) or a control group (CG, n = 7). EG performed flywheel squats and lateral depth jumps three times per week, while CG maintained regular training. Pre- and post-intervention testing included countermovement jumps, reactive strength index (RSI_DJ), force asymmetry, time-to-stabilization, SSC efficiency, and energy transfer ratio (ETR), measured via force plates, EMG, and inertial sensors. Methods: Multi-dimensional statistical analysis revealed coordinated improvements in explosive power and movement efficiency following eccentric training that were not visible when examining individual measures separately. Athletes in the training group showed enhanced neuromechanical control and developed more efficient movement patterns compared to controls. The analysis successfully identified distinct performance profiles and demonstrated that the training program improved explosive characteristics in elite table tennis players. Results: Univariate ANOVAs showed no significant Group × Time effects for RSI_DJ, ETR, or SSC_Eff, although RSI_DJ displayed a moderate effect size in EG (d = 0.47, 95% CI [0.12, 0.82], p = 0.043). In contrast, MANOVA confirmed a significant multivariate Group × Time interaction (p = 0.013), demonstrating integrated neuromechanical adaptations. Regression analysis indicated lower baseline CMJ and RSI_DJ predicted greater RSI improvements. Conclusions: In conclusion, eccentric–reactive training promoted multidimensional neuromechanical adaptations in elite racket sport athletes, supporting the use of integrated monitoring and targeted eccentric loading to enhance lateral explosiveness and efficiency. Full article