体操运动员落地时踝关节损伤生物力学机制的实验与计算机仿真研究

Gymnasts need to land with aesthetics, stability and safety after high-difficulty aerial movements, but they have to face the most serious threat, ankle injury. Epidemiological studies have suggested that gymnastics ranks the second injury rate for all sports. Ankle injury, such as ligamentous sprains, ligamentous or bone fractures, and impingement syndromes, is the highest injury among gymnastic injuries. Sound understanding the causes and mechanism of injury is vital to take measures for preventing the injury. It has been claimed that there are many factors affecting ankle injury, but the injury mechanism is not clear yet. Firstly, this proposal project will experimentally investigate biomechanical characteristics of neuromuscular system of elite gymnasts, which includes joint strengths and proprioceptions to angles in lower limbs, and reaction times to external signals. The subjects will be 30 elite gymnasts. Then, kinematics, kinetics, and surface electromyography (sEMG) of a few key landing movements performed by the elite gymnasts will be studied to investigate relationships between biomechanics and injury occurrences. These key landing movements will have been selected before the biomechanical tests among the routines that easily cause ankle injury. After that, a gymnast-specific multi-rigid body model for simulating gymnastic landing will be developed based on biomechanical, physiologic and anatomic parameters of the gymnasts. After incorporating the experimental data into the model, dynamics of the key landing movements will be analyzed with ground reaction forces (GRFs), lower limb joint forces, and joint torques obtained. In the mean time, a gymnast-specific finite element model of ankle will be developed based on computerized tomography (CT) and magnetic resonance imaging (MRI) data of the ankle, and the dynamic distributions of stress, strain, and strain rate of the ankle tissues during landing will be analyzed as well. According to the landing mechanical variables, such as GRFs, joint forces, joint torques, stresses, strains, and strain rates sustained, the risk of ankle injuries will be estimated. Finally, based on actual injury cases and the two models, a serial of computer simulations will be performed to analyze effects of the factors on risk of ankle injuries under landing loads. The factors include biomechanical characteristics of neuromuscular system, ankle injury history, landing techniques, and physic parameters of apparatuses. The physic parameters of apparatuses will be ground or mat stiffness, damping coefficient, friction coefficient, and dimension. This work would expand our knowledge of the mechanism of ankle injury during gymnastic landing, and further provide new scientific basis for injury prevention and performance enhancement.

体操运动员完成高难度空中动作后要完美、稳定和安全的落地，但落地引起的踝关节损伤是他们面临的最大危险。影响落地时踝关节损伤的因素很多，但其生物力学机制仍不清楚。本课题首先实验测量分析优秀体操运动员神经肌肉系统（下肢关节力量、关节本体感觉和反应时间）和关键落地动作的生物力学特征；然后结合运动员的落地实际动作、生理解剖和力学参量建立落地动作的多刚体系统模型，并对关键落地动作进行动力学分析，获取地面反作用力、关节力/力矩等指标；同时基于运动员CT和MRI数据，建立踝关节有限元模型，计算分析关键落地动作载荷下踝关节的应力、应变和应变率的变化；最后通过计算机仿真方法，并结合实际损伤案例，探讨运动员神经肌肉系统特征、踝关节损伤史、空中和落地动作技术、环境力学特征等因素对踝关节负荷以及损伤危险性的影响。研究结果将为理解体操运动员踝关节损伤机制带来新认识，对体操运动员损伤的预防和动作技术的改进提供科学依据。

体操运动员训练或比赛中每个动作都以落地结束，但损伤发生率很高，且踝关节损伤是发病率最高的部位。本项目在前期研究基础上，首先提出了体操运动员内外危险因素和损伤机制的踝关节损伤发生的综合模型；然后在实验室、训练和比赛现场三种逐步复杂且真实化环境中进行体操运动员不同难度的落地动作实验测试；最后，以实验和测试结果为基础，在多刚体模型和有限元模型两个层次，建立运动员落地及踝关节生物力学模型，并将两个模型进行有机地结合，通过计算机仿真研究，探讨体操运动员落地踝关节损伤的机制。.本项目主要结果为：（1）文献综述表明，体操运动员踝关节损伤与组织负荷阈值、器械和规则、动作以及损伤事件中踝关节负荷特征有关。（2）体操运动员承受的落地冲击随高度增加而增大，并且更高的落地会增加下肢关节屈曲角度；后空翻落地冲击要远高于垂直落地的，且落地站稳的难度更大。（3）体操落地动作控制具有鲜明的特点：触地前先屈曲下肢；触地后初期，下肢关节快速主动屈曲以缓冲落地冲击；落地后期，增加下肢关节力、伸肌力矩、刚度和肌肉激活程度来抵抗落地冲击。（4）运动员下肢负荷随着难度动作增加而快速增大，下肢损伤危险性也会显著增加；高难度落地时采取双脚不同步落地减缓冲击策略，但可能引起更大的损伤风险。（5）自由操两个空翻动作连接动作的第1次落地比第2次落地的下肢负荷较大，但两次的左侧负荷下肢负荷比右侧都大很多。（6）自由操落地垫刚度、阻尼的变化会引起自由操落地动作和下肢负荷的改变，增加摩擦会大大增加关节力、力矩和做功等内部负荷。（7）对现役国家体操队运动员CT和MRI扫描，建立足踝有限元模型；分析表明，落地冲击时，踝关节面前缘和内、外踝等区域应力较大，腓骨下端的外踝变形最大，这可能是距骨前缘增生，内、外踝应力性骨折的原因。.本研究将有助于更好地理解体操运动员踝关节损伤的力学机制，为科学训练、器械改进、临床治疗和康复提供有力的科学依据。