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第一 运动的击球原理(第1页)

第一节网球运动的击球原理

一、击球力量

(一)击球力量的含义

击球动作是球类运动中常见的一种运动形式。比如说,排球的扣球、发球,羽毛球、高尔夫球、棒球运动中的挥拍(棒)击球动作及足球的踢球动作等,网球也不例外。这些用手或手持器械击打动作的特征,是通过击打动作对球或物体施以冲击力,使球或物体产生运动速度的过程。从这些动作系列的发力特点来看,似如鞭打力学原理。从解剖学的角度来讲,首先是力量较大的下肢或躯干部位大肌群开始发力,再依次传到末端的小肌群。在这个意义上,体育运动中的所有投掷动作都很类似。从力学角度来讲,它们大都是碰撞运动。在网球运动中,所谓击球力量大,实际上是指物理学中的动量(mV)变化大。用手或器械运动所产生的冲击力作用于球或物体一定的时间,也就是说力(F)在一定时间(t)作用于球,该球动量的变化等于冲量。因为球体本身的质量是固定的,所以,击球力量大的外在表现形式就是球向前飞行的速度快。可用下面公式表示:

Ft=mv-mv0①

假设初速度为零,式①可用式②表示:

F=mvt②

通过式②可以知道,动量一定时,作用时间越短冲力就越大。

(二)大力量击球的作用

大力击球的作用包括以下方面:

1.要求接球者的动作迅速,否则就会来不及调整动作;

2.力量大的来球,对接球者球拍的作用力较大,这就增加了接球的难度;

3.大力击球,球速较快,接球者会因看不清球而只能凭经验估计它的走向和时间,易判断失误。

(三)加大击球力量的方法

提高参与工作的肌肉力量以加大击球瞬间的挥拍速度,是增强击球力量的关键。为此,应注意以下几个方面:

1.注意腿、腰、上臂、前臂、手腕力量的协调配合,击球瞬间应有爆发力;

2.动作合力方向应尽量向前,避免有相反方向的分力,注意触球瞬间适当减少对球的摩擦力,应向前用鞭打力击球;

3.掌握合理的击球时机和击球位置,以便身体各肌肉群发挥最大效用;

4.适当加大动作半径、增加引拍距离;

5.击球前,发力肌肉应尽量拉长且放松;

6.遵循身体肌肉发力的正常顺序:下肢带动躯干—躯干带动上臂—上臂带动前臂—前臂带动手腕,最终把力传递到球拍,以发挥各关节点的加速作用。一次击球后,应迅速放松,注意动作还原,以便于下一拍球的发力。

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