李大银/吕小军下蹲式挺举关键技术生物力学分析--2019年世界举重锦标赛破世界纪录动作诊断

Biomechanical Analysis of Key Points in Typical Techniques of Squat Clean and Jerk of LI Dayin and LYU Xiaojun--Diagnosis ofWorld Record Breaking at the 2019 WorldWeightlifting Championships

目的:分析李大银和吕小军下蹲挺两类典型技术关键环节的生物力学特点,揭示动作结构与运动功能的生物力学关系。方法:定点定焦摄像、三维录像解析及对比研究。结果:1)“高挺”和“下蹲挺”均可以达到较高水平,需要运动员基于自身特点选择合适的技术。2)提铃至胸阶段和上挺阶段的关键技术是完成“接铃”时段的身体姿态控制,尤其是膝角和髋角控制,2次接铃相互衔接,“高挺”需强大的上肢及腰背爆发力,“下蹲挺”需强大的深蹲能力。3)在下蹲接铃时段,吕小军屈膝和屈髋角速度显著大于李大银,表明其具有更强的下肢伸膝伸髋肌群抗离心收缩能力;在起立站稳时段,李大银伸膝和伸髋角速度显著大于吕小军,表明其具有更强的伸膝伸髋肌群向心收缩能力。4)准备姿势:两人均对上挺准备姿势进行了调整,李大银握距不变、站距变宽,吕小军站距不变、握距变宽。不同的调整方式体现了不同的技术特点,但都有利于降低杠铃所需送达高度,以减小做功。5)技术稳定性:吕小军对杠铃重心轨迹控制较好,杠铃横移距离极小;李大银则控制不理想,杠铃横移距离过大。结论:1)李大银和吕小军都具备第32届夏季奥运会夺冠的实力,前者年轻,成绩提升空间较大,需要提高技术稳定性;后者在如何保持实力和避免伤病方面将面临较大挑战。2)李大银控制杠铃重心轨迹垂直向上的技术有待科技攻关,杠铃横移距离过大提示其双侧力量或发力可能存在不平衡,需要进行双侧动力学测试和力量评估,查找非技术性原因。

Objective:To analyze the biomechanics of two typical techniques of squat clean and jerk performed by LI Dayin(LI)and LYU Xiaojun(LYU)to demonstrate the biomechanical relationship between motion structure and function.Methods:Fixed-focused cameras,three-dimensional video analysis and comparative analysis were used.Results:1)Both“up jerk”and“squat jerk”led to high-level performance,and the athletes needed to choose appropriate techniques based on individual characteristics.2)The key technique of clean stage and jerk stage was the posture control of“catch-bell”motion,especially the control of knee and hip angles.During the connection of two“catch-bell”motions,the“up jerk”emphasizes explosive force of upper limbs and lower back,while the“squat jerk”highlights superior ability of deep squat.3)The comparison of angular velocity of knee and hip:The angular velocity of knee and hip flexion of LYU were significantly larger than that of LI while squatting and catching the bell,indicating higher eccentric contraction ability of knee and hip extensors;the angular velocity of knee and hip extension of LI were significantly larger than that of LYU while standing up,indicating higher concentric contraction ability of knee and hip extensors.4)The comparison of preparation postures:Both of them adapted their preparation postures.LI widened feet distance while keeping holding distance;LYU widened holding distance while remaining feet distance.The difference suggested different characteristics in technique for the consistent purpose of reducing the lifting height of the bell to minimize the work.5)The comparison of technique stability:LYU showed better control on the center of gravity(COG)trajectory of the bell resulting in slightly medial-lateral displacement;LI exhibited larger medial-lateral displacement.Conclusions:1)LI and LYU have the potential to win the first place in the 32th Summer Olympic Games.Improvement in technique stability is required for LI and there is higher rising possibility for him due to his younger age;how to maintain capacity and reduce injuries challenges LYU;2)LI’s technique for regulating the COG trajectory vertically upward should be investigated scientifically.The larger medial-lateral displacement of the bell indicates a possibility of unbalance in strength between bilateral limbs,the cause of which can be detected by bilateral kinetic measurements and strength estimations.