## 4 Discussion  
Although both the lead jab and the rear cross are considered straight punches, their execution techniques differ significantly in terms of biomechanics. The lead jab is a fast punch, typically initiating combinations--its speed partly arises from the short distance between the extended front hand and the target. Typically, it aims to open the opponent's guard and create space for the rear-cross punch, which differs significantly in terms of kinetic properties. Through body rotation and engagement of greater mass and more body segments, the rear cross is able to generate significantly greater Total_GRF. Additionally, it turns out that accelerations occurring with the rear cross can be greater than with the lead jab, which could also be due to the additional torso rotation [16]. In practice, the biomechanical differences between these two punches have a significant impact on their effectiveness and application in combat. The lead jab, with its speed and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Indicator** & **Coefficient (b*)** & **Std. Error of b* & **Coefficient (b)** & **Std. Error of b** & **t(100)** & \(p\)**-Value** \\ \hline Intercept & - & - & \(-\)2642.187 & 934.245 & \(-\)2.828 & 0.006 * \\ \hline Fist Acceleration & 0.679 & 0.101 & 13.29 & 1.986 & 6.693 & \textless{}0.001 * \\ \hline Forearm Acceleration & \(-\)0.007 & 0.093 & \(-\)0.145 & 1.878 & \(-\)0.077 & 0.938 \\ \hline Arm Acceleration & \(-\)0.014 & 0.081 & \(-\)0.266 & 1.498 & \(-\)0.178 & 0.859 \\ \hline Target Contact Time & 0.064 & 0.067 & 1153.517 & 1206.245 & 0.956 & 0.341 \\ \hline Strike Duration (s) & 0.165 & 0.066 & 2231.891 & 891.515 & 2.503 & 0.014 * \\ \hline Age & 0.133 & 0.103 & 7.798 & 6.013 & 1.297 & 0.198 \\ \hline Body Mass & 0.415 & 0.104 & 10.491 & 2.634 & 3.984 & \textless{}0.001 * \\ \hline Body Height & 0.121 & 0.097 & 7.332 & 5.867 & 1.25 & 0.214 \\ \hline Training Tenure & 0.198 & 0.093 & 15.662 & 7.334 & 2.135 & 0.035 * \\ \hline \hline \end{tabular} Note: The dependent variable is Total_GRF. The model’s overall fit statistics are R = 0.801, R\({}^{2}\) = 0.642, Adjusted R\({}^{2}\) = 0.610; F(9,100) = 19.9, * \(p\) < 0.001, with a standard error of the estimate at 289.3.  
\end{table} 
Table 2: Multiple Regression Analysis Results for Total_GRF (pressure force). ability to open the guard, can be used to control distance and initiate attacks, while the rear cross, with its strength and power generated by body rotation, may be more effective in inflicting serious damage and finishing a fight. Understanding these biomechanical differences allows a boxer to better utilize each of these punches depending on the situation and the objective of the attack [17] It is recommended that athletes enhance their training process with advanced technique exercises, especially incorporating body rotation during striking, as this can lead to higher fist acceleration values. The total ground reaction force averaged 1709.28 \(\pm\) 486.62 N for the rear cross and 1176.55 \(\pm\) 248.69 N for the lead jab. The highest recorded values of force were 2866.76 N for the rear cross and 1748.19 N for the lead jab. Therefore, significant differences in striking force between these two techniques were observed. However, considering that the study participants were elite athletes with a high level of training, their results may not fully represent their potential. In studies by [PERSON] and [PERSON], a group of elite boxers achieved a result of 3158 \(\pm\) 1467 N for the rear cross [5]. Meanwhile, [PERSON]'s striking force for the lead jab was 1507.99 \(\pm\) 411 N [18]. [PERSON] [19] reported the peak strength observed ranged from 761 to 1162 N, which is below the values reported by [PERSON] [20], which lie between 1990 and 4741 N, and also lower than the findings of [PERSON] [21], where strength varied from 2471 to 4236 N. Such large differences could be due to the measurement method--in the aforementioned studies, athletes used a fist in a boxing glove.