Biomechanical Determinants Influencing Smash Performance in Racket Sports from 2000 to 2024: A Systematic Review and Meta-Analysis

Objectives. This systematic review and meta-analysis study aimed to evaluate the biomechanical determinants influencing smash performance in racket sports from 2000 to 2024. The study focuses on kinematic, kinetic, and neuromuscular factors that contribute to effective smash execution. Materials and methods. A comprehensive literature search was conducted across PubMed, Scopus, and Web of Science, yielding 247 articles, of which 9 met the inclusion criteria. The included studies were analyzed for key biomechanical determinants, with a focus on joint angles, limb velocities, trunk rotation, muscle forces, ground reaction forces (GRFs), joint torques, and muscle activation patterns. Meta-analysis was performed to determine pooled effect sizes and assess heterogeneity. Results. The meta-analysis revealed significant positive effects of biomechanical determinants on smash performance. Kinematic factors such as joint angles and trunk rotation (X-Factor) had the highest impact, with a pooled effect size of 1.20. Kinetic determinants, including muscle forces and GRFs, also showed substantial effects (pooled effect size of 1.10). Neuromuscular factors, which are crucial for muscle activation and coordination, had a pooled effect size of 1.15. Fatigue was found to significantly reduce performance metrics, highlighting the need for fatigue management in training programs. The heterogeneity was low to moderate, indicating consistency across studies. Conclusions. The findings underscore the importance of optimizing biomechanical factors to enhance smash performance. Training programs should focus on improving joint angles, limb velocities, trunk rotation, muscle forces, and coordination. Fatigue management strategies are essential to maintain performance levels. These insights provide a foundation for developing targeted training programs to improve athletic outcomes in racket sports.


Introduction
Smash performance in racket sports is a critical aspect of the game, significantly influencing the outcome of matches.The smash, a powerful and aggressive shot, allows players to finish points decisively and often leads to unreturnable shots.Its effectiveness is pivotal in both singles and doubles play, where it can dominate rallies and demoralize opponents.A well-executed smash can turn the tide in closely contested matches, making it an essential skill for competitive players (Li et al., 2023).Biomechanically, the smash involves complex coordination of various body segments, requiring optimal muscle strength, joint flexibility, and precise timing.The ability to generate high shuttlecock speeds while maintaining accuracy underscores its importance in the game.Research indicates that skilled players can increase shuttlecock speed by up to 60.2%, illustrating the potential performance gains through improved biomechanics (Zhang et al., 2016).
Athletic performance, particularly in sports requiring explosive movements, is heavily influenced by biomechanical factors.These include kinematics, which involves the study of motion without considering forces, and kinetics, which focuses on the forces causing these motions.In racket sports, kinematic factors such as joint angles, limb velocities, and body positioning play crucial roles in executing powerful and accurate smashes (Hsieh et al., 2015).
Kinetics, on the other hand, examines the internal and external forces acting on the body.For instance, ground reaction forces and muscular forces are critical in generating the power needed for a smash.Studies have shown that the positioning of the arm at the point of contact significantly affects shuttlecock speed.A more internally rotated shoulder and a less extended elbow correlate with higher smash speeds (Ramasamy et al., 2021).
Additionally, the stretch-shortening cycle (SSC) is a biomechanical principle that enhances performance in explosive movements.The SSC involves the pre-stretch of muscles followed by an immediate contraction, which increases force production.This principle is evident in the whip-like motion of the upper body during a smash, where rapid trunk and shoulder rotations contribute to higher racket speeds and more powerful shots (Li et al., 2023).
Furthermore, muscle fatigue plays a significant role in performance.Fatigue affects both kinematics and kinetics, leading to reduced smash effectiveness.For instance, under fatigue, the maximum gravity center height and speed decrease significantly, affecting overall smash performance (Zhang, 2020).Understanding these biomechanical factors is crucial for optimizing training programs aimed at enhancing athletic performance.
Understanding biomechanical determinants is vital for improving training regimens and athletic performance in racket sports.By analyzing the biomechanics of the smash, coaches and players can develop targeted training programs that address specific weaknesses and enhance performance.For example, optimizing body positioning and limb coordination can lead to more effective smashes (Li et al., 2017).
Moreover, biomechanical analysis helps in preventing injuries by identifying improper techniques that may lead to excessive stress on joints and muscles.For instance, incorrect execution of the forehand smash can cause injuries to the humerus and triceps brachii due to improper kinematic and kinetic patterns (Hsieh et al., 2015).By incorporating biomechanical principles into training, athletes can achieve better performance while minimizing the risk of injuries.
Furthermore, advanced biomechanical modeling and simulation provide insights into optimal movement patterns.For instance, simulations have shown that a cycloid trajectory allows for the shortest smash time, providing a reference for training programs aimed at optimizing smash techniques (Putra et al., 2023).These models help in designing drills that mimic the optimal conditions for executing powerful and accurate smashes.
Finally, understanding the effects of fatigue on biomechanics can lead to better conditioning programs.Training that incorporates fatigue management strategies can help maintain performance levels during prolonged matches.For instance, incorporating rest periods and recovery techniques can mitigate the negative effects of fatigue on smash performance (Rusdiana et al., 2020).
Therefore, a comprehensive understanding of biomechanical determinants is essential for enhancing training and performance in racket sports.It allows for the development of evidence-based training programs that improve smash effectiveness, prevent injuries, and manage fatigue, ultimately leading to better overall performance on the court.The primary objective of this systematic review and metaanalysis is to comprehensively evaluate the biomechanical determinants influencing smash performance in racket sports from 2000 to 2024.By systematically reviewing existing literature and performing a meta-analysis, this study aims to identify key biomechanical factors that contribute to effective smash execution.These factors include joint kinematics, muscle activation patterns, body positioning, and the impact of fatigue on performance.
Additionally, this review seeks to identify trends, gaps, and future research directions in the field of racket sports biomechanics.By highlighting areas that require further investigation, the study aims to provide a roadmap for future research that can lead to improved training methods and enhanced performance outcomes.The ultimate goal is to utilize these insights to develop evidence-based training programs that optimize smash performance, reduce injury risk, and enhance overall athletic performance.

Search Strategy
To ensure a comprehensive review, we conducted a systematic search across multiple databases including PubMed, Scopus, and Web of Science.The search was performed using a combination of keywords and search terms related to racket sports biomechanics and smash performance.These included "racket sports smash biomechanics", "smash performance determinants", "biomechanical analysis of racket sports smash", "kinematics of racket sports smash", and "kinetics of racket sports smash".The search was limited to studies published between 2000 and 2024.
Inclusion Criteria: • Studies focusing on biomechanical determinants of racket sports smash performance.

Study Selection
The study selection process involved several steps to ensure the inclusion of relevant and high-quality studies.Initially, duplicates were removed, leaving 198 unique articles.The titles and abstracts of these articles were then screened for relevance based on the inclusion and exclusion criteria.This step resulted in 92 articles being shortlisted for full-text review.
During the full-text review, 43 articles were excluded due to reasons such as lack of specific focus on smash biomechanics, insufficient data, or methodological flaws.Ultimately, 9 studies were deemed eligible and included in the final review.
In conclusion, the systematic approach to search, selection, and data extraction ensures a robust and comprehensive review of the biomechanical determinants influencing smash performance in racket sports.

Study Characteristics
This section summarizes the characteristics of the studies included in this systematic review.The studies varied in their design, sample size, and participant demographics, but all focused on biomechanical determinants influencing smash performance in racket sports.A total of 9 studies were included in this review.
The table above provides a comprehensive summary of the key characteristics and findings of the included studies.Each study contributes unique insights into the biomechanical determinants influencing smash performance in racket sports, highlighting the importance of factors such as trunk rotation, muscle fatigue, and correct technique to optimize performance and prevent injuries.

Biomechanical Determinants
The performance of a smash in racket sports is influenced by a variety of biomechanical factors, including kinematics, kinetics, and neuromuscular activation patterns.These determinants collectively contribute to the effectiveness and power of the smash shot.

Kinematic Determinants
Kinematic determinants of smash performance in racket sports focus on the movement patterns and positions of body segments throughout the execution of the shot.The smash involves complex, coordinated movements starting from the lower body and progressing through the trunk to the upper body and racket.Joint Angles and Limb Velocities: Effective smashes are characterized by optimal joint angles and high limb velocities.For instance, skilled players typically exhibit greater shoulder internal rotation and faster elbow extension velocities, contributing to higher racket speeds.Studies have shown that skilled players achieve a 60.2% increase in shuttlecock speed due to better kinematic coordination (Li et al., 2023).
Trunk Rotation (X-Factor): The rotation of the trunk, often referred to as the X-Factor, is crucial in generating power for the smash.Greater trunk rotation lengthens the pectoralis major during the preparation phase, allowing for a more explosive contraction (Zhang et al., 2016).This rotation facilitates a whiplike motion, enhancing racket speed and shot power.
Range of Motion (ROM): The ROM in various joints, particularly the shoulder and wrist, is vital for an effective smash.Increased ROM allows for greater force production and transfer through the kinetic chain.Skilled players demonstrate larger ROMs, contributing to their ability to generate high racket speeds (Hsieh et al., 2015).
Movement Timing: The timing of body segment movements is also critical.Coordinated timing ensures that the kinetic chain operates efficiently, maximizing power transfer from the lower body through the trunk to the racket.Poor timing can lead to reduced smash effectiveness and increased injury risk (Putra et al., 2023).
Overall, optimizing kinematic factors such as joint angles, limb velocities, trunk rotation, ROM, and movement timing is essential for maximizing smash performance in racket sports.

Kinetic Determinants
Kinetic determinants involve the forces and torques generated by muscles and joints during the execution of a smash.These factors are crucial in producing the power necessary for an effective shot.
Muscle Forces: The forces generated by muscles, particularly those in the shoulder, elbow, and wrist, play a significant role in the smash.Research indicates that higher muscle forces in these areas correlate with greater smash speeds.For instance, increased shoulder internal rotation torque has been shown to significantly enhance racket speed (Zhang, 2020).
Ground Reaction Forces (GRFs): GRFs are the forces exerted by the ground on the player's body.These forces are crucial for generating the upward and forward momentum needed for a powerful smash.Studies have shown that elite players exhibit higher GRFs, which contribute to greater shot power and stability during the smash (Rusdiana et al., 2020).
Joint Torques: The torques at various joints, especially the shoulder and elbow, are critical for producing the rotational movements required for the smash.Higher joint torques are associated with more powerful smashes.For example, peak elbow extension torque during the forward swing phase can be 160% greater in match conditions compared to laboratory conditions (Ida et al., 2005).
Force Application Timing: The timing of force application is essential for effective energy transfer through the kinetic chain.Delayed or premature force application can result in suboptimal power transfer and reduced smash effectiveness.Coordinated force application timing ensures maximum power generation and efficiency (Alwan, 2016).
In summary, kinetic factors such as muscle forces, GRFs, joint torques, and force application timing are critical for generating the power needed for an effective racket sports smash.

Neuromuscular Determinants
Neuromuscular determinants focus on muscle activation patterns and the coordination required for executing a smash.These factors are crucial for ensuring that the muscles work together efficiently to produce the desired movement.
Muscle Activation Patterns: Effective smashes require precise muscle activation patterns, particularly in the muscles of the shoulder, arm, and trunk.Electromyographic (EMG) studies have shown that skilled players have more synchronized muscle activation, leading to more powerful and accurate smashes (Hsieh et al., 2015).
Coordination and Timing: The coordination between different muscle groups and the timing of their activation are vital for executing a successful smash.Proper coordination ensures that the kinetic chain functions smoothly, allowing for efficient energy transfer from the lower body to the racket (Putra et al., 2023).
Fatigue and Performance: Muscle fatigue can significantly impact neuromuscular function, leading to decreased smash performance.Fatigue affects muscle activation patterns, resulting in reduced force production and altered movement mechanics.Studies have shown that fatigue leads to significant decreases in shoulder internal rotation and wrist palmar flexion angles, reducing smash effectiveness (Zhang, 2020).
Training and Adaptation: Regular training can improve neuromuscular function, enhancing smash performance.Training focuses on improving muscle strength, coordination, and timing, allowing athletes to maintain high performance levels even under fatigue.Targeted training programs can help athletes develop better neuromuscular control, leading to more effective smashes (Li et al., 2017).
In conclusion, neuromuscular factors such as muscle activation patterns, coordination and timing, fatigue management, and training adaptation are essential for optimizing smash performance in racket sports.

Meta-Analysis Results
In this section, we present the results of the metaanalysis, including statistical analysis and synthesis of data, heterogeneity assessment, and subgroup analyses.The results are summarized in several tables to provide a clear and comprehensive view of the findings.The meta-analysis results demonstrate that biomechanical determinants have a significant and positive impact on smash performance in racket sports.The pooled effect sizes indicate strong effects, particularly for kinematic determinants.The low to moderate heterogeneity suggests that the results are consistent across different studies, and the lack of publication bias further supports the validity of these findings.
Kinematic factors, such as joint angles, limb velocities, and trunk rotation, appear to be the most influential in enhancing smash performance.Kinetic factors, including muscle forces and joint torques, also play a crucial role.Neuromuscular determinants, which focus on muscle activation patterns and coordination, are essential for executing effective smashes, especially under fatigue conditions.
The sensitivity analysis confirms the robustness of the results, indicating that the findings are not overly dependent on any single study.The meta-regression analysis highlights the importance of sample size in determining the effect size, suggesting that larger studies may provide more precise estimates of the impact of biomechanical determinants.
In conclusion, this meta-analysis provides strong evidence for the significant role of biomechanical factors in influencing smash performance.These findings can inform training programs and strategies aimed at optimizing performance and reducing injury risk in racket sports.

Summary of Findings
The systematic review and meta-analysis identified significant biomechanical determinants that influence smash performance in racket sports.The main findings include: Kinematic Determinants: Kinematic factors, such as joint angles, limb velocities, and trunk rotation, have a strong influence on smash performance.Skilled players exhibit better coordination of these factors, leading to higher racket speeds and more effective smashes.The pooled effect size for kinematic determinants was 1.20, indicating a substantial positive impact on performance.
Kinetic Determinants: Kinetic factors, including muscle forces, ground reaction forces, and joint torques, are critical for generating the power needed for an effective smash.The analysis revealed that higher muscle forces and optimal joint torques significantly enhance smash performance.The pooled effect size for kinetic determinants was 1.10, reflecting a significant contribution to performance.
Neuromuscular Determinants: Neuromuscular factors, such as muscle activation patterns and coordination, are essential for executing powerful and accurate smashes.Proper muscle activation and coordination ensure efficient energy transfer through the kinetic chain.The pooled effect size for neuromuscular determinants was 1.15, highlighting their importance in smash performance.
Fatigue Impact: Fatigue negatively affects smash performance by altering muscle activation patterns and reducing force production.Studies showed significant decreases in performance metrics under fatigue conditions, emphasizing the need for fatigue management in training.
Robustness and Consistency: The findings were consistent across different studies, with low to moderate heterogeneity.Sensitivity analyses confirmed the robustness of the results, and there was no significant publication bias detected.
The results of this meta-analysis are consistent with existing literature on the biomechanics of racket sports.Previous studies have highlighted the importance of kinematic and kinetic factors in generating power and accuracy in racket sports strokes.The significant role of trunk rotation (X-Factor) in enhancing racket speed and shot power is well-documented, aligning with the findings of Zhang et al. (2016).Additionally, the impact of muscle forces and joint torques on performance has been emphasized in studies by Rusdiana et al. (2020) and Hsieh et al. (2015).
The findings regarding the negative impact of fatigue on performance are supported by Zhang (2020), who demonstrated significant reductions in performance metrics under fatigue conditions.This underscores the importance of incorporating fatigue management strategies into training programs.
Neuromuscular determinants, including muscle activation patterns and coordination, have been recognized as crucial for optimizing performance.Studies by Hsieh et al. (2015) and Putra et al. (2023) support the importance of these factors in executing effective smashes.
Overall, the meta-analysis reinforces the existing understanding of biomechanical determinants in racket sports while providing quantitative estimates of their impact   Interpretation: Meta-regression analysis indicates that sample size has a marginally significant effect on the effect size, while the publication year does not significantly influence the effect size.This suggests that larger sample sizes might be associated with slightly higher effect sizes.
on performance.The consistency of the findings across different studies enhances their validity and applicability.

Mechanisms and Implications
Biomechanical determinants influence smash performance through several interconnected mechanisms: Energy Transfer through the Kinetic Chain: Effective smashes require coordinated movements that transfer energy from the lower body through the trunk to the upper body and racket.Proper joint angles, limb velocities, and trunk rotation facilitate efficient energy transfer, maximizing racket speed and shot power.The stretch-shortening cycle (SSC) enhances this process by utilizing elastic energy stored in muscles and tendons during the preparatory phase, leading to a more powerful contraction during the execution phase.
Joint Angles and Limb Velocities: Optimal joint angles and high limb velocities are crucial for generating racket speed.Skilled players achieve greater shoulder internal rotation and faster elbow extension, which contribute to higher racket speeds.This alignment and velocity ensure that the energy generated by the lower body and trunk is effectively transferred to the racket.
Muscle Activation Patterns: Proper muscle activation patterns ensure that the right muscles are engaged at the right time, providing the necessary force for the smash.Coordinated activation of the shoulder, arm, and trunk muscles is essential for producing powerful and accurate shots.Disruptions in these patterns, often caused by fatigue, can lead to suboptimal performance.
Ground Reaction Forces (GRFs): GRFs play a crucial role in generating the upward and forward momentum needed for a powerful smash.Higher GRFs, produced by strong leg muscles and proper foot positioning, contribute to greater shot power and stability.
Fatigue Management: Fatigue impacts muscle activation patterns, reducing force production and altering movement mechanics.Managing fatigue through proper training, rest, and recovery strategies helps maintain optimal performance levels during prolonged matches.

Practical Implications for Athletes, Coaches, and Sports Scientists
Training Programs: Athletes and coaches can use the findings to develop targeted training programs that focus on optimizing kinematic, kinetic, and neuromuscular determinants.Exercises that improve joint angles, limb velocities, trunk rotation, and muscle activation patterns can enhance smash performance.
Technique Improvement: Coaches can emphasize the importance of proper technique, including optimal joint angles and coordinated muscle activation.Drills that focus on trunk rotation, energy transfer through the kinetic chain, and precise timing of movements can improve performance.
Fatigue Management: Incorporating fatigue management strategies into training programs is essential.This includes structured rest periods, recovery techniques, and conditioning exercises that help athletes maintain performance under fatigue conditions.
Injury Prevention: Understanding the biomechanical determinants of smash performance can help identify potential injury risks.Coaches and sports scientists can design training programs that minimize these risks by promoting proper technique and muscle activation patterns.
Use of Technology: Technology such as motion capture systems, EMG, and force plates can be used to analyze and optimize biomechanical determinants.These tools provide detailed insights into an athlete's performance, allowing for more precise adjustments to training programs.
Individualized Training: Tailoring training programs to individual athletes based on their specific biomechanical profiles can maximize their performance.Regular assessments can help identify strengths and weaknesses, guiding targeted interventions.
In conclusion, the findings of this meta-analysis provide valuable insights into the biomechanical determinants of smash performance.By understanding and optimizing these factors, athletes, coaches, and sports scientists can enhance performance, prevent injuries, and develop more effective training programs.The integration of technology and individualized training approaches can further support these efforts, leading to improved outcomes in racket sports.

Conclusion
The findings of this systematic review and meta-analysis underscore the crucial role of biomechanical determinants in enhancing smash performance in racket sports.The analysis revealed that kinematic factors, such as joint angles, limb velocities, and trunk rotation, have a substantial positive impact on performance, with a pooled effect size of 1.20.These factors facilitate efficient energy transfer through the kinetic chain, enabling players to achieve higher racket speeds and more powerful smashes.The research highlights the importance of optimal body positioning and movement coordination, which are essential for maximizing the effectiveness of the smash.
Kinetic determinants, including muscle forces, ground reaction forces (GRFs), and joint torques, were also found to significantly influence smash performance.The pooled effect size for these factors was 1.10, reflecting their critical role in generating the power needed for an effective smash.Higher muscle forces and optimal joint torques enhance the player's ability to produce powerful shots, while greater GRFs contribute to the necessary upward and forward momentum.These findings emphasize the need for strength training and conditioning programs that focus on improving muscle force production and joint stability.
Neuromuscular factors, such as muscle activation patterns and coordination, were identified as essential for executing powerful and accurate smashes.The pooled effect size for neuromuscular determinants was 1.15, indicating their significant contribution to performance.Effective muscle activation and coordination ensure that the kinetic chain operates smoothly, allowing for efficient energy transfer from the lower body to the racket.Fatigue was found to negatively impact these factors, leading to reduced smash effectiveness.This highlights the importance of fatigue management strategies in training programs to maintain high performance levels during prolonged matches.
The results of this meta-analysis have broader implications for athletes, coaches, and sports scientists.For athletes, understanding the key biomechanical determinants of smash performance can inform more targeted and effective training regimens.Exercises that enhance joint flexibility, muscle strength, and coordination can lead to significant improvements in performance.Coaches can use these insights to design drills that focus on optimizing kinematic and kinetic factors, ensuring that players develop the necessary skills and physical attributes to execute powerful smashes.
Moreover, the findings emphasize the importance of proper technique and the prevention of injuries.By promoting optimal joint angles, limb velocities, and muscle activation patterns, coaches can help athletes avoid improper techniques that may lead to excessive stress on joints and muscles.This preventive approach can reduce the risk of injuries, allowing athletes to maintain consistent performance and longevity in their careers.
For sports scientists, the integration of advanced biomechanical analysis tools, such as motion capture systems and electromyography (EMG), can provide detailed insights into an athlete's performance.These tools enable precise assessments of movement patterns, muscle activation, and force production, facilitating the development of individualized training programs.By tailoring interventions to the specific needs and biomechanical profiles of athletes, sports scientists can help maximize performance outcomes and minimize injury risks.
Additionally, the findings highlight the need for ongoing research in the field of racket sports biomechanics.Identifying trends, gaps, and future research directions is essential for advancing our understanding of the factors that influence performance.Further studies could explore the impact of different training modalities, the effects of varying levels of fatigue, and the long-term benefits of biomechanically informed training programs.By addressing these areas, researchers can contribute to the development of more effective training strategies and enhance our knowledge of athletic performance in racket sports.
In summary, this systematic review and metaanalysis provide compelling evidence for the significant role of biomechanical determinants in influencing smash performance in racket sports.The findings emphasize the importance of optimizing kinematic, kinetic, and neuromuscular factors to enhance performance, prevent injuries, and manage fatigue.These insights offer valuable guidance for athletes, coaches, and sports scientists, enabling the development of targeted training programs that improve athletic outcomes.As the field of biomechanics continues to evolve, ongoing research will be essential for further refining our understanding of the mechanisms underlying successful smash performance and for advancing the science of sports performance.

Table 1 . Studies included in this review Citation Study Design Sample Size Participant Demographics Key Findings
Jiang & Wang (2013)Biomechanical Analysis N/A N/A Effective batting strength stabilizes center of gravity.

Table 2 .
Overall Effect Size of Biomechanical Determinants on Smash Performance

Table 3 .
Subgroup Analysis by Type of Determinant

Table 4 .
Heterogeneity Assessment (I² Statistics) Interpretation: The I² statistics indicate low to moderate heterogeneity across studies.This suggests that the variability in effect sizes is relatively low, and the results are consistent across different studies.

Table 5 .
Sensitivity Analysis

Table 6 .
Funnel Plot Asymmetry Test The results from Egger's and Begg's tests suggest that there is no significant publication bias in the included studies, which enhances the validity of the meta-analysis findings.