# Biomechanics of Punching--The Impact of Effective Mass and Force Transfer on Strike Performance
## 4 Discussion  
The results of this study provide new insights into effective mass in four fundamental boxing techniques: jab, cross, lead hook, and rear hook. The analysis of body mass transfer efficiency in punches revealed significant differences between straight punches and hooks, which could be crucial for optimizing training and increasing punching power. Our findings suggest that the most effective punches in boxing are not necessarily the strongest or the fastest but rather those that optimize force transfer. High effective mass values for straight punches--particularly the cross (31.17 \(\pm\) 16.20 kg) and jab (30.39 \(\pm\) 15.09 kg)--indicate their greater biomechanical efficiency in transferring body mass into the punch. Despite their lower peak force output, these punches demonstrated significantly higher effective mass and Effective Mass Index values compared to hooks, suggesting that straight punches allow for a more effective transfer of body mass. This suggests that boxers can utilize their body mass more effectively when delivering linear punches, which may result from a more direct force transmission through the kinetic chain, which other authors called \"stiffening\" of the muscles in a moment of contact with a target [14]. Traditional boxing theory has often associated punch effectiveness with acceleration and the fighter's mass [6]. However, our results show that impulse decreases as acceleration increases, suggesting that overly fast punches may limit force transfer efficiency. The jab exhibited the highest impulse value, averaging 63.80 \(\pm\) 15.36 Ns, indicating that this punch maintains force application over a more extended duration. The cross followed closely with an impulse of 57.90 \(\pm\) 11.82 Ns, reinforcing the efficiency of straight punches in sustaining impact over time. This may explain why experienced boxers often 'hold' their fist on the target for a fraction of a second instead of delivering punches with unchecked speed [9]. The regression analysis confirmed that effective mass (\(\beta\) = 0.98, \(p\) < 0.001) is the strongest predictor of punching force, reinforcing its dominant role in force transmission. This further supports the idea that straight punches allow for a more efficient transfer of body mass into impact, as they maximize force through proper kinetic chain utilization. Straight punches engage the entire kinetic chain in a more linear and controlled manner compared to hooks. This allows the force generated by leg and hip movement to be efficiently transmitted through the torso and arm to the fist, maximizing the effective mass of the punch. The strong correlation between impulse/fist acceleration and effective mass indicates that not the total impulse but its adjustment to acceleration determines punch effectiveness. This suggests that boxers should focus on optimizing joint stiffness at the moment of impact rather than merely increasing force or speed [14]. The Kruskal-Wallis test revealed a significant difference between the jab and cross for impulse (KW-H = 214.06, \(p\) < 0.001, \(\eta^{2}\) = 0.426), suggesting that while both straight punches effectively transfer force, the jab maintains a higher total impulse. Straight punches are also more directional, reducing energy losses from lateral movements and improving the mechanics of force application [15]. This corresponds with other research findings, where it has been observed that precise control of the moment of impact affects the effectiveness of force transfer [11]. An analysis of kicking mechanics in Kyokushin karate revealed that strikes to a target generate significantly higher acceleration values than kicks in the air, confirming the key role of biomechanical synchronization in optimizing strike force [16]. Similar findings were obtained before [4], emphasizing that straight punches allow for optimal utilization of ground reaction forces and better control of torque.