Li Shangxiao, Yuan Shufang, Shi Yi, Ni Bin, Guo Wenxia, Yang Chaopeng, Wang Mingzhi, Hao Weiya
Research Center for Sports Psychology and Biomechanics, China Institute of Sport Science, Beijing, China.
Department of Health Service, Logistics University of People's Armed Police Force, Tianjin, China.
Front Bioeng Biotechnol. 2024 Sep 3;12:1450953. doi: 10.3389/fbioe.2024.1450953. eCollection 2024.
Sharp force injury has been and will remain to be a major cause of violent death; however, scientific evaluations on the impact of body posture of the victim and gender of the perpetrator on sharp force injury have been scarce. The purpose of this study was to evaluate the biomechanical characteristics found in individuals (male and female) when using a Chinese kitchen knife to slash the neck of a dummy while it was in the standing and supine positions. This work offers a solid basis for forensic identifications, criminal investigations, and court trials.
A total of 12 male and 12 female college students participated in this study. Kinematic, kinetic, and surface electromyography (sEMG) data were evaluated when slashing the neck of a dummy while it was in the standing and supine positions using a Chinese kitchen knife.
When slashing the neck of a standing dummy, participants showed shorter contact time (19.5%) and slower shoulder velocities (30.9%) as well as higher hip velocity (26.0%) and increased root mean square (RMS) and integral electromyography (iEMG) for the anterior deltoid (51.3% and 51.2%, respectively) compared to those while the dummy was in the supine position (all < 0.05), regardless of gender. When slashing a dummy's neck while it was in standing and supine positions, male participants showed higher shoulder, elbow, and wrist velocities (22.6%, 22.7%, and 24.4%, respectively) and higher slashing velocity (19.8%), slashing force (24.2%), and energy (46.2%) than female participants (all < 0.05). In addition, male participants showed shorter contact time (17.8%), and the values of RMS and iEMG of the anterior deltoid, biceps brachii, extensor carpi radialis longus, and flexor carpi ulnaris were less than those of female participants (98.9%, 47.3%, 65.6%, and 33.4% for RMS and 115.1%, 59.4%, 80.1%, and 47.8% for iEMG, respectively).
There was no difference in slashing speed, slashing force, and energy when using a Chinese kitchen knife to slash the dummy's neck while it was in different body postures (standing and supine), suggesting a similar level of injury severity. However, there were significant differences in slashing action patterns between the two body postures, with longer contact time, smaller hip velocity, greater shoulder velocity, and less muscle activation level of the deltoid exertion when slashing the dummy's neck in the supine position. Gender may have a greater effect on the severity of slashing, and the gender difference may be partly related to the body weight difference. The findings from this study may provide quantitative indicators and references for analyzing the motive behind the crime, as well as for case reconstruction, and for the court's conviction and sentencing processes.
锐器伤一直是并仍将是暴力死亡的主要原因；然而，关于受害者身体姿势和犯罪者性别对锐器伤影响的科学评估却很匮乏。本研究的目的是评估使用中式菜刀在假人处于站立和仰卧姿势时砍击其颈部的过程中，男性和女性个体所呈现出的生物力学特征。这项工作为法医鉴定、刑事调查和法庭审判提供了坚实基础。
共有12名男性和12名女性大学生参与了本研究。在使用中式菜刀砍击处于站立和仰卧姿势的假人颈部时，对运动学、动力学和表面肌电图（sEMG）数据进行了评估。
在砍击站立假人的颈部时，与砍击仰卧假人相比，参与者的接触时间更短（缩短了19.5%），肩部速度更慢（降低了30.9%），而髋部速度更高（提高了26.0%），三角肌前部的均方根（RMS）和积分肌电图（iEMG）增加（分别增加了51.3%和51.2%），无论性别如何（所有P值均<0.05）。在砍击处于站立和仰卧姿势的假人颈部时，男性参与者的肩部、肘部和腕部速度更高（分别高22.6%、22.7%和24.4%），砍击速度（高19.8%）、砍击力（高24.2%）和能量（高46.2%）均高于女性参与者（所有P值均<0.05）。此外，男性参与者的接触时间更短（缩短了17.8%），三角肌前部、肱二头肌、桡侧腕长伸肌和尺侧腕屈肌的RMS和iEMG值均低于女性参与者（RMS分别低98.9%、47.3%、65.6%和33.4%，iEMG分别低115.1%、59.4%、80.1%和47.8%）。
使用中式菜刀砍击处于不同身体姿势（站立和仰卧）的假人颈部时，砍击速度、砍击力和能量没有差异，这表明损伤严重程度相似。然而，两种身体姿势之间的砍击动作模式存在显著差异，在仰卧姿势下砍击假人颈部时，接触时间更长，髋部速度更小，肩部速度更大，三角肌用力时的肌肉激活水平更低。性别可能对砍击的严重程度有更大影响，性别差异可能部分与体重差异有关。本研究结果可为分析犯罪动机、案件重建以及法庭定罪和量刑过程提供定量指标和参考。
