Aboodarda Saied J, Byrne Jeannette M, Samson Michael, Wilson Barry D, Mokhtar Abdul H, Behm David G
1School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada; 2Center for Biomechanics, National Sports Institute, Bukit Jalil, Kuala Lumpur, Malaysia; and 3Sports Medicine Unit, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
J Strength Cond Res. 2014 Aug;28(8):2314-23. doi: 10.1519/JSC.0000000000000498.
Previous investigators have speculated that applying additional external load throughout the eccentric phase of the jumping movement could amplify the stretch-shortening cycle mechanism and modulate jumping performance and jump exercise intensity. The aims of this study, therefore, were to determine the effect of increased eccentric phase loading, as delivered using an elastic device, on drop jumps (DJs) performed from different drop heights. Of specific interest were changes in (a) the kinetics; eccentric and concentric impulse, rate of force development (RFD), concentric velocity and (b) the electromyographic (EMG) activity of leg muscles. In a randomized repeated-measure study, 15 highly resistance trained male subjects performed DJs from 3 heights (20, 35, and 50 cm) under 3 different conditions: body weight only (free DJ) and with elastic bands providing downward force equivalent to 20% (+20% DJ) and 30% (+30% DJ) of body mass. All DJs were recorded using video and force plate data that were synchronized with EMG data. Results demonstrated that using additional tensile load during the airborne and eccentric phases of the DJ could enhance eccentric impulse (p = 0.042) and RFD (p < 0.001) and resulted in small to moderate effect size (ES) increases in quadriceps intergrated EMG across the eccentric phase (0.23 > ES > 0.51). The observed greater eccentric loading, however, did not immediately alter concentric kinetics and jump height nor did it alter muscle activation levels during this phase. The findings indicated that, in addition to the conventional technique of increasing drop height, using a tensile load during the airborne and eccentric phases of the DJ could further improve eccentric loading of DJs. As it has been suggested that eccentric impulse and RFD are indicators of DJ exercise intensity, these findings suggest that the loaded DJs, using additional elastic load, may be an effective technique for improving DJ exercise intensity without acute effects on the jumping performance and neuromuscular activation level in highly trained athletes.
以往的研究人员推测，在跳跃运动的离心阶段施加额外的外部负荷，可以增强拉长-缩短周期机制，调节跳跃性能和跳跃运动强度。因此，本研究的目的是确定使用弹性装置增加离心阶段负荷对从不同高度进行的纵跳（DJ）的影响。特别感兴趣的是（a）动力学方面的变化；离心和向心冲量、力发展速率（RFD）、向心速度，以及（b）腿部肌肉的肌电图（EMG）活动变化。在一项随机重复测量研究中，15名经过高度抗阻训练的男性受试者在3种不同条件下从3个高度（20厘米、35厘米和50厘米）进行纵跳：仅体重条件下（自由纵跳），以及使用弹力带提供相当于体重20%（+20%纵跳）和30%（+30%纵跳）的向下力条件下。所有纵跳均使用与EMG数据同步的视频和测力台数据进行记录。结果表明，在纵跳的腾空和离心阶段使用额外的拉伸负荷可以增强离心冲量（p = 0.042）和RFD（p < 0.001），并导致股四头肌在整个离心阶段的积分EMG有小到中等程度的效应量（ES）增加（0.23 > ES > 0.51）。然而，观察到的更大离心负荷并没有立即改变向心动力学和跳跃高度，在此阶段也没有改变肌肉激活水平。研究结果表明，除了增加下落高度的传统技术外，在纵跳的腾空和离心阶段使用拉伸负荷可以进一步改善纵跳的离心负荷。由于有人提出离心冲量和RFD是纵跳运动强度的指标，这些发现表明，对于训练有素的运动员，使用额外弹性负荷的负重纵跳可能是一种有效的技术，可提高纵跳运动强度，而不会对跳跃性能和神经肌肉激活水平产生急性影响。
