## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Range** & **r-Value** & \(\boldsymbol{p}\) & N \\ \hline Flying distance (m) & 2.81–4.73 & 0.08 & 0.43 & 26 \\ Ball height (m) & 0.61–1.41 & 0.21 & 0.31 & 26 \\ Flying time (s) & 0.31–0.65 & \(-\)0.03 & 0.54 & 26 \\ \hline \multicolumn{5}{c}{\(\boldsymbol{\mu}\pm\)**SD**} \\ \hline Max head speed (m/s) & 7.34 \(\pm\) 0.45 & 0.37 & 0.05 & 26 \\ Head speed at impact (m/s) & 6.63 \(\pm\) 0.70 & 0.59 & 0.00 & 26 \\ Head speed drop (\%) & 4.93 \(\pm\)4.27 & \(-\)0.77 & 0.00 & 26 \\ Time offset (\%) & 26.29 \(\pm\) 20.56 & \(-\)0.67 & 0.00 & 26 \\ \hline \hline \end{tabular} \(\mu\): average, SD: standard deviation.  
\end{table} 
Table 2: The characteristics of the selected parameters and their relationship with ball speed enhancement (BSE) revealed by correlation analysis. BSE, indicating its pivotal role in achieving diving header effectiveness. The unexpected 4.93% head speed drop at impact adversely affected momentum transfer. This result indicates that minimizing the head speed drop enlarges BSE. Further, the confirmed high negative correlations of head speed drop and time offset with BSE highlight the importance of minimizing speed drop and temporal disparities for improved momentum transfer and header effectiveness. The drop in head speed and time offset during the diving header may be attributed to head and neck movements, likely associated with the final coordination/adjustment for accurate heading. Biomechanically, this adjustment in a multi-segment system, such as the human body, reduces system rigidity, resulting in a decrease in effective mass during impact. Effective mass, defined as the mass that would exhibit equivalent motion characteristics if substituted for the multi-segment system, is a parameter often used in quantifying impact in human movement [36; 37]. Previous studies [38; 39; 40] demonstrate that effective mass during impact depends on player body mass and technique/movement, with a stiffer joint connection leading to higher effective mass. In soccer heading, the theoretical estimation [40] shows that the effective mass for an ideal vertically jumping header is one-half of the body mass, while for an ideal diving header, it is 100% of the body mass. Torso alignment with impact direction is considered a method to increase effective mass [39; 41]. Additionally, by applying a pre-tensed condition on neck muscles, additional mass is recruited from the torso, raising the effective mass of the system during head impact and, thus, increasing ball speed during impact [42; 43; 44]. In a non-stiff condition (e.g., the adjustment movement for accurate heading), the opposite happens. The effectiveness of diving headers is a multi-factorial issue tied to the spatial and temporal demands of soccer. Diving headers have the potential to extend the attacking range, making them valuable for practitioners and a versatile tool in the soccer playbook for both offensive and defensive purposes. Coaches and players can leverage these biomechanical insights to inform training strategies. However, the observed head speed drop and time offset during the diving header could be counterproductive, diminishing part of the skill's effectiveness. As stated before, the negative influences are likely related to the motor control of head and neck movements preceding impact, suggesting a detrimental consequence of the final coordination or adjustment for accurate heading. Training programs could focus on minimizing speed drop and refining the coordination of temporal aspects to increase the overall effectiveness of the diving header. In summary, the factors and aspects discussed above can be incorporated into coaching practices to formulate specific training regimens. The biomechanical insights derived from this pioneering study have the potential to optimize the training of diving headers, enhancing their overall effectiveness.