拦阻着舰过程中不同百分位人体颈部损伤风险的差异对比

目的对比拦阻着舰过程中不同百分位人体颈部损伤风险的差异。方法利用已建立的人椅背带系统动力学模型和头颈部力学模型,采用文献中典型拦阻着舰过程座椅底部的加速度曲线作为输入条件,开展数值仿真,验证模型的正确性,并得到假人颈部各关节的轴向力、剪切力和弯矩等力学参数。结果第95百分位假人的剪切损伤N_(km)指数高于第5百分位假人。假人上、下部颈椎的N_(ij)指数小于0. 2,N_(km)指数约为0. 65。结论在拦阻着舰过程中,人体颈部更容易产生由于关节剪切力导致的损伤。研究结果可为评估不同百分位人体在典型拦阻着舰过程中的颈部损伤风险提供数据支持。     

座椅椅背倾角对飞行员颈部损伤的影响

目的 探究不同椅背倾角对飞行员颈部损伤的影响。方法 基于头颈部多刚体动力学模型,对两种典型飞行工况下(急转弯和稳定盘旋)椅背倾角17°和22°进行仿真计算,得到颈部肌肉力及椎间力,并采用颈部损伤的NIC准则、N_ij准则和简明损伤分类方法对颈部损伤进行评估与预测。结果 同一飞行工况下,椅背倾角17°时,颈部前屈,斜方肌和头夹肌受到拉伸。椅背倾角22°时,颈部后伸,集总舌肌受到拉伸,且椅背倾角17°时斜方肌受到的拉力最大。同一颈椎节段,椅背倾角17°时的轴向力高于椅背倾角22°时,而22°时的后伸力矩大于17°时的前屈力矩。所有飞行工况下的力和力矩均未超过颈椎节段的损伤评估值,颈部脊髓也不会发生损伤。急转弯工况下,椅背倾角为22°时C7～T1节段N_ij在所有工况中最大,达到航空领域建议的临界值,此时颈部发生中度、重度伤的概率分别为3.93%、2.63%。结论 本研究结果可为评估椅背倾角对飞行员颈部的损伤情况提供支撑。     

汽车后碰撞时人体头颈部的动力学响应及损伤分析

目的建立基于人体解剖学结构的精细化头颈部有限元模型,研究不同后碰撞速度下颈部损伤。方法该模型以人体头颈部CT扫描图像为基础,利用Mimics进行三维骨重建,通过Hyper Mesh完善颈部三维实体韧带、小关节等组织,并进行网格划分。生成的模型包括头部、8节椎骨(C1～T1)、6个椎间盘(包括纤维环、髓核和上下软骨终板)、小关节(包括软骨和关节囊韧带)、韧带、肌肉等结构,最后在有限元后处理软件中完成模型验证与后碰撞计算。结果分别对模型进行轴向冲击、前后屈伸和侧屈模拟并与实验数据对比,验证模型的有效性,并进行速度为20、40、60、80 km/h后碰撞计算。在20 km/h速度下,颈部无损伤出现,在40、60、80 km/h速度下,最早出现损伤的都是韧带。随着速度增加,颈部各组织受力不断增大。速度为80 km/h时,颈椎的密质骨、松质骨和纤维环最大应力分别为226. 4、11. 5、162. 8 MPa,当韧带应变达到极限时,开始出现撕裂。结论所建头颈部有限元模型具有较高的生物仿真度和有效性,可用于交通事故中颈部损伤分析的研究,在一定程度上有助于颈椎损伤的诊断、治疗和预防。     

起床过程中腰椎应力动力学响应

目的揭示起床过程中腰椎间盘的应力响应特征。方法根据实验数据,建立并验证考虑材料非线性和各向异性属性的全腰椎有限元模型,在此基础上模拟并计算人体从仰卧、起身、左转到坐在床沿完整过程中腰椎主要结构的应力分布和动态变化情况。结果起床过程中腰椎间盘纤维环、髓核及终板的应力大小和分布不断变化,各节段的应力集中在背侧,L4~5上最大,应力峰值出现在当躯干从仰卧起转过35°~62°之时,分别是坐稳时的3倍、仰卧时的17倍。结论 L4~5椎间盘后侧是损伤和退变高发区,在日常活动中实际承受的应力可能要比以往按静态测算的应力更高,影响范围也更大。动力学模拟能更全面深入地了解腰椎间盘的负载特点,为防治相关腰椎疾病提供科学依据。     

飞行员机动飞行过程中颈椎动力学响应仿真及损伤预测

目的 采用有限元方法针对典型机动飞行动作过程中飞行员颈椎动力学响应进行仿真,并采用冲击损伤及疲劳损伤模型对飞行员颈椎组织损伤失效进行分析预测。方法 构建具有较高生物仿真度的颈部有限元模型,结合实例对模型的有效性进行验证。加载离心训练机不同模式下的过载曲线进行数值仿真,并采用通用颈椎损伤判定准则和生物组织疲劳损伤模型对组织的冲击损伤及疲劳损伤进行预测分析。结果 机动飞行动作下,过载冲击产生的椎骨、椎间盘最大应力分别为66.53、58.63 MPa,根据N_ij损伤准则计算得到最大N_ij为0.096,低于损伤耐受阈值1,不会对颈椎骨组织造成直接的急性损伤;引用生物组织疲劳损伤模型得知,松质骨在不间断重复加载超过40 000次的情况下发生疲劳失效破坏,考虑到飞行员有限的飞行生涯,椎骨骨组织不会因疲劳损伤积累而导致破坏。结论 研究结果在一定程度上有助于制定飞行员训练和飞行方案,也为其防护装备开发提供数据支持。     

军机飞行员的颈部损伤研究

目的调查飞行员的颈部损伤现状,分析导致颈部损伤的因素和飞行员的颈部损伤对飞行训练的影响,为开展相应的生理研究和开发工程解决方案提出建议。方法对1924名军机飞行员进行问卷调查,涉及初教机、强击机、歼击机、轰炸机、运输机及直升机飞行员。调查分为两部分:(1)飞行员基本情况,包括:单位、年龄、机种、飞行时间、身高、体重;(2)颈部损伤情况,包括:颈部症状、颈部症状对飞行的影响、导致颈部损伤的原因等。对调查结果进行统计分析。结果本研究调查表明71.3%的飞行员曾有过颈部不适症状,60.4%的飞行员颈部不适发生在飞行中;有33.7%的飞行员曾有过颈部疼痛症状,19.2%的飞行员的颈部疼痛症状发生在飞行中;飞行加速度、头盔重量及飞行日留空时间过长是导致飞行员颈部症状的主要原因。轰炸机飞行员发生颈部不适和疼痛的比例最高。结论颈部损伤已成为我军飞行员的常见病与多发病,飞行员的颈部损伤已影响到日常的飞行训练,且随着歼、强击机飞行员的飞行载荷及飞行训练强度的增加,飞行员的颈部损伤还会呈上升趋势。因此,应高度重视军机飞行员的颈部损伤问题,对此问题的生理研究及工程解决方案还需进行深入研究。     

空军飞行员颈肌强度的研究

目的 研究空军飞行员颈部各肌群的强度及其在航空动力环境中的意义。方法 采用CME-1飞行员颈肌训练器对149名空军飞行员颈部前、后、左、右肌群进行等长测试。每一个方向测量10次,10次中最大峰值作为该侧肌群的强度;计算每侧10次测试的峰值均值与肌群强度比值,反映飞行员的耐力。结果 空军飞行员前、后、左、右各肌群的强度分别为（132．0±42.2）N、（205.2±82.2）N、（174.3±76.4）N和（191.2±78.3）N,前屈和后伸肌群分别与其他肌群比较有显著性差异（P<0.001）,左、右侧屈肌群之间的比较亦有显著性差异（P＜0.001）,前屈肌群强度最小,后伸肌群强度最大,左右侧肌群强度居中,且右侧肌强度大于左侧。前、后、左、右各肌群反复测试10次的各次最大肌力均值与肌强度之比分别为74.24%、72.86%、72.75%和68.72%。结论 为了充分发挥高性能战斗机的机动性能,最大限度地减少加速度导致的飞行员颈部损伤,应鼓励空军飞行员在地面进行颈肌强度训练,并掌握好飞行过程中头部控制技术。     

头盔质量和质心对军机飞行员颈部肌力的影响

目的研究头盔质量和质心偏移对军机飞行员颈部肌肉活动特性的影响。方法基于AnyBody软件平台建立头颈部肌骨模型,包含C0、C1-7、T1和136组头颈部肌肉。采用集中载荷模拟头盔作用,对不同头盔质量、质心位置和加速度载荷下的7个主要肌群的肌力进行了仿真计算。结果当头盔质心与头部质心重合时,支配后伸的头半棘肌、肩胛提肌、头夹肌和颈夹肌处于收缩发力状态。当头盔质量增大,这些肌群肌力也随之线性增加,并且加速度载荷对肌力增大程度起放大作用。头盔质心后移,会降低后伸肌群的肌力,增大前屈肌群受力。头盔质心左右偏移引起的附加侧弯力矩则会激活支配侧弯功能的肌群的活动。结论头盔质量和质心位置对颈部肌群活动特性有明显影响,本文建立的头颈部肌骨模型可以计算不同状态下肌力的变化,头盔设计和使用过程可采用该技术进行定量分析。     

基于车人碰撞事故重建的行人头部动力学响应

目的 研究行人交通事故中,不同碰撞速度、不同车型及行人不同受撞击部位与行人头部损伤严重度的关系。方法 通过MADYMO多刚体动力学软件对一起有视频的行人交通事故进行事故重建,获得初始和边界条件,然后通过获得的边界和初始条件进行不同车速(20、30、40、50、60 km/h)、不同车型(轿车、SUV型车、面包车)、行人不同受撞击部位(正面、侧面、背面)的模拟碰撞实验,对模拟碰撞实验中行人头部损伤情况进行分析,并利用两例真实行人交通事故对部分结果进行验证。结果 不仅车辆碰撞速度、车辆前置结构影响行人头部损伤严重度,行人受撞击部位也是影响行人头部损伤严重度的重要原因。在碰撞速度≤30 km/h时,行人与地面接触造成的损伤可能比与车辆造成的损伤严重;碰撞速度≥40 km/h时,行人头部损伤主要是与车辆接触所致。结论 利用监控录像能比较准确地开展行人交通事故重建,从而对行人动力学响应进行分析。在行人交通事故频发路段,对不同车型进行不同限速,能有效减小行人头部损伤的严重程度。     

The responses of frog muscle spindles during stimulation of slow motor axons

Summary Responses of muscle spindles of the iliofibularis muscle of the frogLitoria aurea have been recorded during single shock and repetitive stimulation of single functional motor axons. Repetitive stimulation of axons which innervated slow muscle, and on four occasions, axons which innervated twitch muscle, produced a large increase in the dynamic response of the spindle to a ramp-and-hold stretch. While extrafusal slow muscle did not respond to a single motor volley, some spindles did, especially if at the same time the muscle was being stretched. In an explanation of the effect of muscle stretch on responses of spindles to slow motor volleys it was proposed that stretch acted to reduce the internal motion in muscle fibres produced by a non-uniform distribution of sarcomere lengths. It was proposed that this kind of effect may account for dynamic fusimotor actions in all vertebrate spindles.Financial assistance was provided by a grant from the National Health and Medical Research Council of Australia, Grant No. 78/5721     

Simulated and experimental temperature responses in man during exercise in varying environments

Stolwijk's mathematical model of thermoregulation is validated against reported human experience.Computed temperatures from the model were compared against experimental data obtained, using various matched environmental conditions. Three fit male subjects 168.5 ± 1.8 cm, 64.2 ± 1.9 kg, 24.5 ± 2.6 yr. (mean ± range) underwent pre-work and incremented work phases in the various conditions. Measurements of rectal temperature (T_R), tympanic temperature (T_T), and four skin sites ($\text{T}$_S) were taken. Air temperature (T_AIR), air velocity (V), relative humidity (RH) and work (W), were manipulated.Good simulations were achieved at 30°C air temperature, rectal temperature deviation $\text{d}$ < 0.10°C. As lower ambient temperatures were encountered initial transient drop of simulated core temperature was emphasized, and this was not reflected in experimental data. It is proposed that the process of thermoregulation during exercise in the cold requires further conceptual refinement in the model. By subdivision of active muscular layers in the passive system of the model superior simulations at low air temperatures, may be achieved.     

Dynamic control of breathing during exercise and hypercapnia

The dynamic influences of end-tidal CO₂ and exercise on ventilation are compared when CO₂ and exercise are imposed separately and when they are imposed simultaneously. Five human subjects are studied. The subjects performed three trials: random work rate forcing, random CO₂ inhalation and their simultaneous loading. The work rate was varied between 20 and 80 W as a pseudorandom binary sequence. The concentration of inspired CO₂ was varied randomly between 0 and 7 per cent, adjusted so that it produced approximately the same amount of ventilatory fluctuations as the random work load. The relative contribution of each variable was analysed using multivariate autoregressive analysis at frequencies ranging from 0·1 to 1 cycle min⁻¹. The results show that the dynamics of the response to CO₂ inhalation, exercise and their combination are nonlinear and that the combination of CO₂ inhalation and exercise magnifies the nonlinear behaviour. Ventilation is largely unaffected by either work rate or end-tidal CO₂ at 1 cycle min⁻¹. During simultaneous CO₂ and work rate forcing, ventilation tends to follow the change in the end-tidal CO₂.     

侧向冲击载荷作用下髋护具对股骨-骨盆复合体生物力学响应的影响

目的利用三维有限元法研究髋部护具对人体股骨-骨盆复合体在侧向冲击载荷作用下生物力学响应的影响。方法基于中国力学虚拟人模型库建立股骨-骨盆-软组织复合体的三维有限元模型,包括皮质骨、松质骨和软组织,并在此基础上建立髋部护具和股骨-骨盆-软组织复合体系统的三维有限元模型;同时,在两个模型中构建刚体平面仿真地面。约束地面刚体,对两个模型均施加侧向2 m/s的速度载荷,整个仿真分析时间设定为20 ms。通过三维有限元分析计算获得两模型受侧向冲击载荷过程中应力、应变变化特性,对比分析髋部护具对股骨-骨盆复合体生物力学响应的影响。结果髋部护具使股骨-骨盆复合体在侧向冲击载荷作用下的应力峰值出现时间提前4 ms以上,且应力应变水平出现大幅度降低;皮质骨上的应力峰值降低67.88%以上,松质骨上的峰值应力下降69.34%以上,松质骨上的压缩主应变峰值降低可达63%。结论在侧向冲击载荷作用下,髋部护具对股骨-骨盆复合体具有良好的保护作用,能够有效预防骨折的发生或降低骨折风险。     

Role of reflex responses of knee musculature during the swing phase of walking in man

Summary Muscle activation patterns of the quadriceps and hamstrings were studied in normal human subjects walking at comfortable speed on a treadmill. In addition knee angular velocity patterns and swing and stance phases of the step cycle were recorded. Data were collected from normal paces and from paces in which a momentary unexpected resistance was applied to the leg during swing. The application of the resistance caused an advance in the onset of both quadriceps and hamstrings activity. The latency of the onset of activity following the resistance in the quadriceps was 78.2±26.4 ms and this was considered to indicate a long latency stretch reflex. There was a close association between the onset of quadriceps and hamstrings activity both in the normal and resistance paces. The changes observed in knee angular velocity upon application of the resistance indicate tight control of angular velocity patterns. The results have important implications regarding neural control of muscle during purposive movement and the regulation of sensitivity of muscle receptors during such movements, especially during the periods when the muscle is normally inactive. Supported in part by grant from the Medical Research Council of Ireland     

Dynamic responsiveness of lumbar paraspinal muscle spindles during vertebral movement in the cat

Muscle spindles provide essential information for appropriate motor control. In appendicular muscles, much is known about their position and movement sensitivities, but little is known about the axial muscles of the low back. We investigated the dynamic responsiveness of lumbar paraspinal muscle spindle afferents from L₆ dorsal root filaments during constant velocity movement of the L₆ vertebra (the feline has seven lumbar vertebrae) in Nembutal-anesthetized cats. Actuations of 1 mm applied at the L₆ spinous process were delivered at 0.5, 1.0 and 2.0 mm/s. The slow velocity component was measured as the slope of the relationship between displacement during the constant velocity ramp and instantaneous discharge frequency. The quick velocity component was the slope’s intercept at zero displacement. The peak component was determined as the highest discharge rates occurring near the end of the ramp compared with control. The slow velocity component over the three increasing velocities was 23.9 (9.9), 21.6 (9.6) and 20.5 (9.5) imp/(s mm) [mean (SD)], respectively. The quick velocity component was 28.4 (8.6), 31.4 (9.8) and 35.8 (10.6) imp/s, respectively. These measures of dynamic responsiveness were at least 5–10 times higher compared with values reported for appendicular muscle spindles. The peak component’s velocity sensitivity was 2.9 (imp/s)/(mm/s) [0.2, 5.5, lower, upper 95% confidence interval] similar to that for cervical paraspinal muscles as well as appendicular muscles. Increased dynamic responsiveness of lumbar paraspinal muscle spindles may insure central driving to insure control of intervertebral motion during changes in spinal orientation. It may also contribute to large, rapid and potentially injurious increases in paraspinal muscle activity during sudden and unexpected muscle stretch.     

Experimental muscle pain results in reorganization of coordination among trapezius muscle subdivisions during repetitive shoulder flexion

The aim of the study was to examine the effect of experimental unilateral upper trapezius muscle pain on the relative activation of trapezius muscle subdivisions bilaterally during repetitive movement of the upper limb. Surface EMG signals were detected from nine healthy subjects from the upper, middle and lower divisions of trapezius during a repetitive bilateral shoulder flexion task. Measurements were performed before and after injection of 0.5 ml hypertonic (pain condition) and isotonic (control) saline into the upper division of the right trapezius muscle in two experimental sessions. On the painful side, upper trapezius showed decreased EMG amplitude (average rectified value, ARV) and lower trapezius increased ARV throughout the entire task following the injection of hypertonic saline (40.0 ± 22.2 vs. 26.0 ± 17.4 μV, and 12.5 ± 7.6 vs. 25.6 ± 14.8 μV, respectively, at the beginning of the contraction). On the side contralateral to pain, greater estimates of ARV were identified for the upper division of trapezius as the task progressed (37.4 ± 20.2 vs. 52.7 ± 28.4 μV, at the end of the contraction). Muscle fiber conduction velocity did not change with pain in all three divisions of the right trapezius muscle. The results suggest that local elicitation of nociceptive afferents in the upper division of the trapezius induces reorganization in the coordinated activity of the three subdivisions of the trapezius in repetitive dynamic tasks.     

Dynamic properties of renshaw cells: Equivalence of responses to step changes in recruitment and discharge frequency of motor axons

In decerebrate cats, the dynamic responses of Renshaw cells to step changes in input were determined seperately both for changes in the number of -axons excited and for changes in the frequency at which they were stimulated. Together, these two input variables to the Renshaw cells describe the level of activity in the motor output from the spinal cord.In either case, the dynamic responses of the interneurons depend only on their static activity before and after an input step occurs, but are otherwise indistinguishable. This favors the interpretation that the two input variables are equivalent under dynamic conditions, i.e., Renshaw cells respond to total motor output.Our friend and colleague Alfred Kuschmierz died on 17 October 1981 at the age of 29