## 3 Results  
The outcomes of the analysis concerning smash quality exhibit statistically highly significant disparities (\(p\) < 0.01) across all three parameters associated with smash quality, as shown in Table 2. With progressive years of training, there is a noteworthy increment of 60.2% in the maximum flight velocity (V\({}_{\text{max}}\)), while conversely, the shuttlecock clearance height (H\({}_{\text{p-n}}\)) and the flight angle at release (A\({}_{\text{shuttle}}\)) experience substantial reductions of 485.0% and 212.2%, respectively. The enhancements in the quality of the smash are evidently linked to alterations in full-body control mechanisms, as illustrated in Figure 2. Notable distinctions encompass (a) the distinction between skilled players who employ jumping techniques during the smash and novice players who do not, (b) the absence of a complete full-body tension-arc formation in novice groups, (c) the heightened degree of trunk rotation observed in the skilled group, and (d) a 2D follow-through (in the sagittal plane) in novices versus a follow-through with the arm-racket crossing in front of the body in the skilled group. The determinants, denoting kinematic parameters that exhibited significant modifications due to years' training for smash optimization, are quantitatively determined in this study. Figure 3 and Table 3 detail the statistically significant variations identified in the investigation. \begin{table}
\begin{tabular}{c c c c c} \hline
**Smash Quality** & **Novice Group** & **Skilled Group** & \(p\)**-Value** & **Change (\%)** \\
**Parameter** & & & & \\ \hline V\({}_{\text{max}}\) (m/s) & 36.7 \(\pm\) 8.5 & 58.8 \(\pm\) 9.9 & \textless{}0.00 & 60.2 \\ H\({}_{\text{p-n}}\) (m) & 1.17 \(\pm\) 0.84 & 0.20 \(\pm\) 0.16 & \textless{}0.00 & \(-\)485.0 \\ A\({}_{\text{shuttle}}\) (\({}^{\circ}\)) & 18.8 \(\pm\) 11.8 & \(-\)21.1 \(\pm\) 4.6 & \textless{}0.00 & \(-\)212.2 \\ \hline \end{tabular} \(\text{V}_{\text{max}}\): Maximum shuttlecock speed, H\({}_{\text{p-n}}\): shuttlecock clearance height, A\({}_{\text{shuttle}}\): shuttlecock flight angle at release.  
\end{table} 
Table 2: Training effects revealed by smash quality parameters. Firstly, the novice group displayed inconsistent positioning (Figure 3b-d) in contrast to the consistent positioning observed in the skilled groups (Figure 3a,b). The degree of consistency is determined by the horizontal distance (D\({}_{\text{c-s}}\)) between a player's center of gravity (COG) and the shuttlecock at the moment of impact. Secondly, the novice group exhibited an upward return (A\({}_{\text{shuttle}}\) in Table 2) resulting from a racket angle of 108\({}^{\circ}\) relative to the horizontal direction at the moment of impact (A\({}_{\text{racket}}\) in Table 3), whereas the skilled group executed a downward return due to a 61\({}^{\circ}\) A\({}_{\text{racket}}\). Thirdly, when compared to the novice players, the skilled group displayed a substantial 75.7% augmentation in trunk rotation (X-factor in Table 3, 24.7\({}^{\circ}\) vs. 43.4\({}^{\circ}\)). Fourthly, the range of motion (ROM) in shoulder flexion/extension and abduction/adduction was increased by 175.5% and 231.7%, respectively, when comparing the skilled group to the novices (shoulder flex/ext in Table 3, 25.3\({}^{\circ}\) vs. 69.7\({}^{\circ}\) and shoulder abd/add in Table 3, 8.2\({}^{\circ}\) vs. 27.2\({}^{\circ}\)). Fifthly, the ROM in shoulder rotation was nearly threefold (increased almost two times) in the skilled group when compared to the novice group (shoulder rotation in Table 3, 65.7\({}^{\circ}\) vs. 185.4\({}^{\circ}\)). Sixthly, in contrast to the novices, the skilled group exhibited a notable 70.8% increase in the ROM of elbow flexion/extension (elbow flex/ext in Table 3, 48.9\({}^{\circ}\) vs. 83.5\({}^{\circ}\)). Lastly, the skilled group demonstrated a substantial 48.7% expansion in the ROM of wrist flexion/extension relative to the novice group (wrist flex/ext in Table 3, 94.4\({}^{\circ}\) vs. 140.4\({}^{\circ}\)).