半蹲式着陆中脊柱承受作用力和力矩的逆向动力学分析

Reverse kinematics analysis of spine torque and force during simulated half-squat parachute landing

目的通过空降兵平台跳伞着陆测试,运用逆向动力学方法计算着陆过程中脊柱承受的作用力及力矩,分析脊柱致伤动力学原因,为科学指导跳伞训练提供理论依据。方法 23名现役空降兵,男性,无脊柱及四肢外伤病史,平均身高(175.78±2.34)cm,平均体重(71.05±4.73)kg。受试者以标准的空降兵半蹲式着陆姿势分别由高40 cm、120 cm的平台跳落。Vicon三维运动捕捉系统记录运动过程,通过三维测力平台测量地面反作用力。利用人体仿真模型系统(AnyBody Modeling System)建立空降兵人体脊柱及下肢的生物力学仿真模型,将数据以C3D格式导入仿真模型并进行动力学分析。测试参数包括脊柱上、下端力矩及腰椎各节段的关节反作用力。比较受试者脊柱上端及下端所受力矩峰值在不同跳台高度时的差异,以及相同跳台高度时受试者脊柱上与下端所受力矩峰值的差异。结果不同跳台高度时受试者脊柱上端间及下端间所受力矩差异均无统计学意义(P>0.05)。相同跳台高度时,受试者脊柱下端旋转力矩、侧弯力矩较上端增加,差异有统计学意义(Z=2.972~4.107,P<0.01);脊柱上下端屈伸力矩差异无统计学意义(P>0.05)。与40 cm跳台时比较,120 cm跳台时受试者腰椎各节段受到的垂直作用力、剪切力(L3-L4除外)增加,差异具有统计学意义(t=3.525~4.873,P<0.01);只有T12-L1的侧方应力增加显著(t=2.293,P<0.05)。相同跳台高度时,腰椎各椎体关节垂直方向的作用力是由下至上逐渐减小;脊柱上、下端前后方向剪切力方向相反,呈现大致对称分布,各节段间总体差异有统计学意义(F=70.651、85.101,P<0.01);脊柱左右侧方应力较弱,各节段间差异无统计学意义(P>0.05)。结论①头颅与颈椎、腰椎与骨盆的相对稳定有助于避免损伤,提高脊柱周围肌肉的强度是必要的。②垂直作用力、前后剪切力是造成腰痛的主要原因。③应科学组织训练,提高冲击耐受力和空间本体感觉能力。

Objective To analyze the kinematics of causing spine injury by calculating the force and torque applied on spine with reverse kinematics method upon the simulated parachute landing test,and to provide theory base for the guidance of parachuting training.Methods Twenty-three male active paratroopers without extremity trauma or spinal diseases volunteered to participate in this study.Their average height was(175.78±2.34)cm and average weight was(71.05±4.73)kg.All subjects respectively jumped from 40 cm-and 120 cm-platforms with a standard half-squat posture to the land point.The Vicon 3D motion capture system was used to record the jump process and the AMTI 3D force measuring platform was used to measure the ground reaction force.The biomechanical simulation model of spine and lower limbs was established by AnyBody Modeling System.All the experimental data were introduced into the model with the C3D format for kinematics and kinetics analysis.The measurements included the upper and lower spine torque and joint reaction force of lumbar segments.The maximum torque was compared between different height jumps and between the upper and lower spine ends in same height jumps.Results The torques measured from the upper and lower spine ends had no statistical significance in both height jumps(P>0.05).The maximum rotational torque and lateral torque of lower spine were significantly larger than those of upper spine in same height jumps(Z=2.972-4.107,P<0.01),while the flexion and extension torques were not statistically different between two height jumps(P>0.05).Compared to 40 cm jump,the vertical and the shearing forces on the lumbar segments(excluding L3-4)significantly increased in 120 cm jump(t=3.525-4.873,P<0.01),and the lateral force significantly increased at T12-L1 segment(t=2.293,P<0.05).In the same height jumps,the vertical reaction forces on bottom-up lumbar segments decreased gradually.The anteroposterior shearing forces were in opposite directions at upper and lower spine ends and symmetrical distributed,and showed statistical significance among segments(F=70.651,85.101,P<0.01).The right and left lateral forces of spine were weak and showed insignificance among segments(P>0.05).Conclusions①Maintaining the stability of head,cervical spine,lumbar spine and pelvis would be helpful to avoid injuries.It's necessary to improve the strength of the muscles surrounded spine.②The vertical and anteroposterior shearing forces would be the main reason led to low back pain.③The ground training method should be more scientific to improve the impact tolerance and spatial perception.