【作者】 周家颖；

【导师】 王清；

【作者基本信息】 上海体育学院 ， 体育教育训练学， 2008， 博士

【摘要】 研究目的:跳深是发展下肢肌肉快速力量的常用练习。研究跳深时下肢肌肉的生物力学特征,无论是在丰富力量训练的理论体系上,还是在满足力量训练的实际需求上,都具有重要意义。通过对运动员在不同下落高度和不同运动状态跳深时的运动学、动力学和下肢8块肌肉EMG的测试结果分析及讨论,建立起运动员跳深时下肢肌肉的生物力学特征框架结构,以期为运动训练实践提供有价值的理论参考。研究方法:本研究的主要方法为测试法。采用Kistler三维测力台(采样频率500Hz)、TM-6710CL高速摄像机(拍摄频率120f/s)和16道便携式无线遥测表面肌电测试系统(采样频率1000Hz)对在正常状态与相对疲劳状态下(完成较大负荷练习之后)完成不同下落高度跳深的运动员进行了同步测试。研究与受试对象为田径跳跃项目的12名三级运动员和12名一级运动员。研究结果:1.正常状态下跳深时,足着地前下肢肌肉的“预激活”模式因人而异;运动员下肢肌肉“预激活”的个体模式,不随跳深下落高度的变化而发生本质性的变化。2.跳深时,下肢着地缓冲时间小于蹬伸时间,髋关节角度变化最小,踝关节角速度的变化幅度最大;下肢起主要作用的肌肉首先是伸膝肌肉,其次是踝跖屈肌肉,然后才是伸髋肌肉;伸膝关节的三块肌肉中,股内侧肌和股外侧肌所起的作用大于股直肌。在“适宜”下落高度跳深时,下肢肌肉的缓冲能力和蹬伸能力能得到最大程度的发挥,再跳起高度最高。在“过高”下落高度跳深时,下肢各关节缓冲幅度加大,着地阶段缓冲时间和耦联时间延长,影响下肢伸肌群由离心收缩向向心收缩转换的速度和完整动作的顺利进行。3.随跳深下落高度的增加,力峰值出现的时间越早,力峰值出现的时间占着地阶段时间的比例越小。在“过高”下落高度跳深时,力值变化的显著特征是力峰值较高,并伴随力值的快速下降。在“适宜”下落高度跳深时,体现下肢肌肉缓冲能力和蹬伸能力强弱的缓冲结束时刻的力值最大。下肢肌肉的离心收缩活动能力在肌肉的拉长-缩短周期收缩活动中起着重要的作用。重视下肢肌肉“退让”工作能力的训练,并加强下肢肌肉“退让”工作能力与快速蹬伸能力相结合的整体性训练,是跳深训练的关键。4.下肢所测大多数肌肉缓冲期的表面肌电均方根振幅值和平均积分肌电值均大于蹬伸期的。正常状态时,同一名运动员下肢所测肌肉在不同下落高度跳深时,所表现出的EMG变化趋势和肌肉协调模式是一致的,不随跳深下落高度的变化而发生本质的变化。不同运动员在同一下落高度跳深时,同名肌肉的EMG活动强度和变化趋势存在差异,尽管这块肌肉在下肢肌肉活动时所起的作用相同。5.相对疲劳状态下(完成较大负荷练习之后),运动员跳深时的着地时间、缓冲时间和耦联时间延长,再跳起高度明显下降;其髋、膝、踝关节的动作顺序与正常状态下的相比发生改变,膝关节的运动滞后;所测肌肉EMG的平均功率频率值下降,运动员下肢肌肉的用力特征、所测肌肉的“预激活”模式、肌肉协调模式、动作过程中做功的比值和肌肉间的协同关系发生变化,下肢肌肉力量明显下降。6.下肢肌肉的基础力量和完成技术动作的能力,是引起三级运动员跳深时在生物力学指标上与一级运动员之间存在较大差距的主要原因。加强运动员下肢肌肉的基础力量训练,改善中枢神经系统对下肢肌肉的反射性调节能力,循序渐进地提高跳深下落高度,是提高跳深训练效果的有效途径。7.跳深训练前,应根据训练目的和运动员下肢肌肉的基础力量水平选择“适宜”的跳深下落高度,合理安排不同下落高度跳深训练的比例,科学安排跳深的组数、间歇时间和训练前的准备活动,加强跳深训练后的恢复,切忌安排运动员在相对疲劳状态下(完成较大负荷练习之后)进行跳深训练。8.“适宜”的跳深下落高度、缓冲与蹬伸动作衔接快且协调、再跳起高度高,是评价跳深动作质量的重要标准。更多还原

【Abstract】 Purpose: Drop jumping is a frequently used exercise to develop explosive muscle power of the lower leg. A research on the biomechanical features of the lower leg muscles in drop jumping not only enriches the theoretical system for power training but also satisfies the needs of practical training. Through an analysis and discussion on the kinematics, dynamics and the EMG activity of the eight muscles in the lower leg, set up a biomechanical features structure of the lower leg muscles in drop jumping.Methods: This study employed a 3D Kistler Force Measurer(500Hz), a TM-6710CL High-speed Video Camera(120f/s), and sixteen Wireless Telemetering EMG Testing Systems(1000Hz) to conduct the simultaneous testing on 12 third-class and 12 first-class athletes performing the drop jumping at different whereabouts heights, and in both normal and relative fatigue states (after heavy loading exercise).Results and conclusions:1. Before landing, the measured muscles in the lower legs have already been“pre-activated.”In the normal state, the“pre-activation”strategies differ from person to person, and the individual’s“pre-activation”modes of the lower legs do not change fundamentally with the change of whereabouts heights.2. In the landing stage, the buffer time is shorter than the extending time, and the change in hip angle is the minimum, whereas the range of ankle angle velocity change is the biggest. The knee-extending muscles in the lower legs play the leading role, and then come ankle muscles, hip stretching muscles. In the three muscles in the knee joints, the vastus medialis muscle and the vastus laterlis muscle play a more important role than the vastus intermedius muscle. At a moderate descending height, the buffer capacities and extending capacities give a fullest display, and the re-jump height reaches its peak value. At a higher whereabouts height, the buffer range of the joints in the lower legs increases and the buffer and coupling time prolongs, which affects the conversion velocity from centrifugal contraction to centripetal contraction and the smooth completion of the action.3. With the increase of the whereabouts height, the earlier the peak force value appears, the smaller the ratio to the time in the landing period. At a higher whereabouts height, the most conspicuous feature of the peak value change is that the higher peak value appears and declines rapidly with the force value. However, at a moderate height, the force value at the moment of buffer finishing, which reflects the buffer capacity and extending strength of the muscles in the lower legs, reaches its peak. The centrifugal contraction capacity of the lower legs plays a very important role in the stretch-shortened cycle of muscle. The key for the drop jumping training is to emphasize the“yielding”capacity of the lower leg muscles, and attach importance to the combination of the“yielding”capacity and high-speed extending capacity of the lower leg muscles in practical training.4. The RMS of EMG for most of the measured muscles of lower limb in the buffer period and the average IEMG of EMG are both bigger than those in the extending period. During the normal state, the same athlete’s active mode of EMG of the muscles measured at different whereabouts height remains the same; it does not change essentially with the changes in whereabouts heights. When different athletes perform drop jumping at the same whereabouts height, the active strength of EMG and changing tendency differ, although the same muscle performs the same function in completing the same intensity work.5. During the relative fatigue state (after completion of heavy loading exercise), the touchdown time, buffer time and coupling time extend; re-jump height decreases tremendously. Compared with that in the normal state, the movement sequence of hip, knee and ankle changes, with the knee movement becoming the last. The MPF of EMG of the muscles measured in the lower limb declines. Changes also happen to the forcibly features, the“pre-activation”modes of the eight tested muscles, EMG movement modes, and the modes of working ratio in the course of movement, and the coordinating modes between muscles. The strength of the lower limb muscles decreases obviously.6. In terms of biomechanical features, the difference between the third-class and first-class athletes is caused by the fact that the third-class athletes’basic strength of the lower limb and the capacity of completing the movement are lower than those of the first-class athletes. The effective approaches to enhance the outcomes of drop jumping practice is to stress the basic strength exercise, and improve the reflective coordinating ability of the central nerves system on lower limb muscles, and to increase the whereabouts height gradually.7. The“moderate”whereabouts height for drop jumping should be determined by the training objectives and athletes’basic strengths of their lower limbs. Deciding on appropriate proportion of various whereabouts heights for drop jumping training, scientific arrangement of the amount and proper intervals between groups of movements as well as pre-training preparation and post-training recovery activities are crucial to drop jumping. Drop jumping in a relative fatigue state, especially after heavy workload, should be avoided.8. Moderate whereabouts height, the rapid and smooth connection between buffer and extending activities, and a high re-jump height are key criteria for assessing the quality of drop jumping performances.更多还原