后仰跌倒人体撞击加速度及冲量分析

目的 测评后仰跌倒过程中身体不同部位冲击加速度的空间分布及时间累积特性。方法招募20~22岁健康青年男、女志愿者各4名，利用3轴加速度传感器测得后仰跌倒全过程头、胸、腰、左/右大臂/手/足、左/右前/后髋、左/右股骨头、骶骨、尾骨的3轴加速度，以第1峰值片段的加速度信号幅度矢量（signal magnitude vector, SMV）进行多项式拟合，分析跌倒过程中全身冲击加速度分布，以及后仰跌倒时头部、髋部相关位点的失重时间、总跌倒时间、SMV峰值、触地相对冲量等跌倒冲击力学参数。结果 左/右后髋、头部后仰跌倒过程中的SMV峰值与相对冲量显著高于其他部位（P＜0.05）；左/右后髋部与地面平行的加速度较大；左/右后髋、左/右股骨头、骶骨、尾骨的转动变换角显著大于其他部位（P＜0.05）。且后仰跌倒过程中，各检测位点均表现出与矢状面呈53.58°±6.75°的滑动趋势。结论 头部与髋关节是后仰跌倒过程中易受伤部位，其失重时间(0.26±0.05) s可作为保护装置最长启动时间；跌倒过程在左/右后髋、左/右股骨头、骶骨、尾骨表现出的大变换角可能是造成扭伤的重要原因。
Objective To evaluate the characteristics of spatial distribution and time accumulation of impact acceleration at different parts of human body during backward falling process. Methods Four healthy men and four healthy women (20-20 years old) were enrolled. The tri-axial acceleration on head, chest, left/right arm/hand/foot, left/right front/back hip, left/right femur head, sacrum and coccyx throughout the backward falling were measured by ADXL335 tri-axial acceleration sensor. Systemic acceleration distribution of backward falling was polynomial fitted by signal magnitude vector (SMV) of its first peak. Besides, parameters of impulse mechanics such as zero-g time, total falling time, peak SMV, relative pressure impulse of the vulnerable sites (head, hip and its related sites) were also calculated. Results Compared with the other parts of the body, the peak SMV and relative impulses of left/right back hip and head were significantly higher (P＜0.05). Acceleration that paralleled to the ground in left/right back hip was also relatively large. The rotational transform angles of left/right back hip, left/right femur head, sacrum and coccyx were significantly larger (P＜0.05). In addition, during the process of falling backward to the ground, a sliding tendency toward the sagittal plane 53.58°±6.75° occurred at all testing sites. Conclusions Head and hips are vulnerable during backward falling, and their zero-g time (0.26±0.05) s can be used as the longest starting time of falling protection devices. The large change angle of left/right hip, left/right femoral head, sacrum and coccyx may be the important cause of the sprain during backward falling.