1.    Introduction
Discus throwing is one of the most complex throwing events in track and field, requiring an optimal combination of strength, coordination, balance, and biomechanical control (1). This skill involves multiple phases, including rotation, weight transfer, and discus release, each requiring precise interactions between linear and angular displacement, velocity, acceleration, and muscular coordination. Success in discus throwing largely depends on the athlete’s ability to generate and efficiently transfer kinetic energy from the lower limbs to the upper body and, ultimately, to the discus. Therefore, a detailed analysis of the kinematic variables associated with this event can significantly contribute to optimizing athletic performance. Previous studies on discus throw kinematics have primarily relied on two-dimensional (2D) analysis, which has provided valuable insights into movement patterns and force application (2). However, these methods fail to capture the full complexity of an athlete’s movements in three-dimensional (3D) space, thereby limiting a comprehensive understanding of the mechanics of discus throwing. This sport involves multi-planar movements, where different body segments operate across various planes (3). For instance, trunk and lower limb rotation occurs in the transverse plane, discus displacement follows a parabolic trajectory, and changes in the center of mass occur in the frontal plane. Consequently, advanced motion analysis techniques, such as 3D kinematic analysis, are essential for a more precise evaluation of athletic performance.
Recent advancements in motion capture technology and 3D kinematic analysis systems have enabled more accurate measurement of movement parameters (4). Studies have shown that these methods allow for a more detailed examination of intersegmental coordination, velocity patterns, and acceleration changes (5, 6). However, most research in this area has focused on elite athletes, with limited data available on amateur throwers, particularly young athletes (7). Understanding kinematic variations during the early stages of training can play a crucial role in optimizing throwing techniques and reducing injury risk (8). Given the limitations of previous research, the present study aims to conduct a more in-depth investigation of 3D kinematic variables in discus throwing. Specifically, this research focuses on analyzing movement during the final throwing phase to determine the relationship between key kinematic parameters and athletic performance. Overall, this study seeks to enhance our understanding of discus throw dynamics and provide valuable insights for designing corrective training programs and educational frameworks (9). Based on these objectives, the study examines three main hypotheses:
1.    The displacement of various body segments significantly correlates with discus throw performance.
2.    Increased velocity and acceleration of the upper body enhance throwing distance.
3.    3D analysis provides more precise information on performance-determining factors compared to 2D methods.
Ultimately, this research aims to offer practical insights into discus throw kinematics, assisting coaches and athletes in refining throwing techniques and improving performance levels..
2.    Methods
This study involved six male discus throwers under 20 years old, selected from athletics clubs in Diyala under the supervision of the national federation. Participants had at least three years of competitive experience, were right-handed to ensure consistency in motion analysis, and had no injuries at the time of data collection. Athletes with musculoskeletal injuries in the past six months or those who failed to complete the required throws were excluded. The study adhered to ethical guidelines, with approval from the University of Diyala Ethics Committee (Approval No. 9802), and informed consent was obtained from all participants. Each athlete performed six legal discus throws following standard competition rules, with the best attempt selected for analysis. Motion was recorded using two high-speed iPhone 14 cameras (60 fps), positioned 1.5 meters high and 8 meters away. Kinematic analysis was conducted using APAS software, with reflective markers placed on key anatomical points (shoulder, elbow, wrist, pelvis, knee, and ankle) for precise motion tracking. Video data were processed using automated and manual digitization techniques to extract kinematic variables such as angular velocity, joint angles, and release mechanics. A 3D calibration frame (1×1×1 m) ensured accurate spatial scaling, and a Butterworth low-pass filter (6 Hz) was applied to reduce noise. Discus throwing was biomechanically divided into four main phases (11). Phase transitions were identified using kinematic markers such as peak hip and shoulder angular velocity and release timing. Performance was measured as the recorded throw distance (meters). Kinematic variables for both limbs (right and left) were analyzed, including linear and angular displacement, velocity, and acceleration at key anatomical points. Data processing was conducted in MATLAB, where a fourth-order Butterworth filter (6 Hz) was applied to reduce noise. Statistical analyses were performed using SPSS (version 26), including descriptive statistics (mean ± SD) and Pearson correlation analysis to examine relationships between kinematic variables and performance. A significance level of p < 0.05 was set for all tests.
3.    Results
This study analyzed six right-handed male discus throwers under 20 years old from Diyala province. The participants had an average age of 20.1 ± 0.24 years, height 175.3 ± 7.58 cm, weight 76.4 ± 2.84 kg, and BMI 24.81 ± 0.69. The results indicated a significant correlation between throwing performance and body segment displacement in the final phase of the throw across all three axes. Additionally, kinematic variables were significantly associated with throwing success (Table 1). The study found a positive correlation between increased velocity in key body segments and greater throw distance (p < 0.05). The highest velocities were recorded in the hand (1223.93 cm/s) and wrist (1060.78 cm/s), highlighting their critical role in discus release. Significant correlations were observed between throwing performance and velocity at the hip (r = 0.973), elbow (r = 0.955), and wrist (r = 0.934), suggesting that higher speeds in these segments improve performance. Lower-body segments such as the foot and ankle also showed strong correlations, emphasizing the importance of force transmission from the ground during the throw. Increased acceleration in key body segments was positively correlated with throw distance (p < 0.05). The highest acceleration values were recorded in the hand (307030.2 cm/s²) and wrist (292965.5 cm/s²), reaffirming their essential role in discus release. Significant correlations were found between throwing performance and acceleration at the hip (r = 0.885), shoulder (r = 0.875), and elbow (r = 0.944), indicating that greater acceleration in these segments contributes to improved performance. Lower-body segments, including the foot and ankle, also exhibited strong correlations, confirming the role of force generation and transmission from the ground. These findings support the biomechanical principle that increased acceleration in both upper and lower body segments enhances the force applied to the discus at release, ultimately improving throw performance. The strong correlation between acceleration and throw distance underscores the importance of kinetic chain activation in maximizing discus throw distance.

4.     Conclusion
This study analyzed key kinematic variables in the final phase of discus throwing and their relationship with athletic performance. Findings indicated that whole-body displacement, velocity, and acceleration significantly impact throwing performance. A strong correlation was observed between hip and shoulder displacement and overall throw performance, aligning with previous studies (13). Moreover, increased linear velocity in the upper body (shoulder, elbow, wrist) was positively associated with throw distance, consistent with findings by Dai et al. (2013) (14). A fundamental principle of throwing biomechanics is the effective transfer of force from the lower to the upper body through the kinetic chain. This study confirmed that increased velocity and acceleration in major joints, such as the hip, shoulder, elbow, and wrist, play a crucial role in improving throw performance, supporting the impulse transfer principle (15) and aligning with findings by Alimjanovna (2024) (16).
Optimal center-of-mass control was also crucial, as athletes who efficiently managed weight transfer achieved greater throw distances (17). Maintaining dynamic balance during the transition from the rotational phase to the throwing phase directly influenced the discus release angle, while poor balance control might reduce optimal velocity and acceleration at release. The 3D approach provided deeper insights into movement patterns compared to traditional 2D analyses. Unlike studies that focused only on sagittal and frontal planes, this research captured full spatial motion, allowing a more precise evaluation of segmental contributions to athletic performance. These findings highlight the importance of advanced motion-capture techniques in training programs for discus throwers (2, 18, 19). The results demonstrated a significant correlation between displacement, velocity, and acceleration along the three axes (x, y, z) and discus throw performance. Additionally, the critical role of intersegmental coordination in force transfer and movement optimization was confirmed. Ultimately, quantitative 3D analysis can enhance discus throwing performance, providing valuable tools for coaches and athletes to refine technique and improve efficiency.

Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be addressed in this research.
Funding
This research did not receive any financial support from government, private, or non-profit organizations.
Authors' contributions
All authors contributed equally to preparing the article.
Conflicts of interest
The authors declare that there are no conflicts of interest associated with this article.