Markovic Goran, Jaric Slobodan
Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.
Med Sci Sports Exerc. 2007 Oct;39(10):1757-64. doi: 10.1249/mss.0b013e31811ece35.
The aim of this study was to evaluate the effect of external loading on mechanics of vertical jumping. We hypothesized that the muscular mechanical output could be higher under no-load conditions than in the presence of either positive or negative external loads.
Fifteen physically active men performed maximal countermovement jumps (CMJ) on a force plate while a pulley system provided approximately constant vertical force acting in a way to either reduce or increase the body weight. As a result, the weight of the body approximately corresponded to the gravity acceleration from 0.70 to 1.30 g (g = 9.81 m.s(-2)).
Regarding the jumping kinematics, we observed a significant (P < 0.001) load-associated decrease in both the peak velocity and lowering of the center of mass during the eccentric jump phase, but not in the duration of the subsequent concentric jump phase. Regarding the muscular mechanical output, both the mean power (P ) and peak momentum (M) revealed significant (P < 0.001) changes associated with loading, and further post hoc analyses revealed significantly higher values (P < 0.05-0.001) of both P and M for 1.00 g compared with most of the other loading conditions applied.
The results suggest that subject's own body provides the optimal load for producing maximum mechanical output in vertical jumping. If corroborated by the results of future studies performed on other rapid movement, our findings could support the hypothesis that the muscular system is designed for producing maximum mechanical output in rapid movements when loaded only with the weight and inertia of its own body.
本研究旨在评估外部负荷对垂直跳跃力学的影响。我们假设在无负荷条件下肌肉的机械输出可能高于存在正向或负向外部负荷时的输出。
15名身体活跃的男性在测力板上进行最大反向运动跳跃（CMJ），同时一个滑轮系统提供大致恒定的垂直力，其作用方式是减轻或增加体重。结果，身体重量大致相当于0.70至1.30 g（g = 9.81 m·s⁻²）的重力加速度。
关于跳跃运动学，我们观察到在离心跳跃阶段，峰值速度和质心下降均与负荷相关且显著降低（P < 0.001），但在随后的向心跳跃阶段持续时间没有变化。关于肌肉机械输出，平均功率（P）和峰值动量（M）均显示出与负荷相关的显著变化（P < 0.001），进一步的事后分析表明，与大多数其他负荷条件相比，1.00 g时P和M的值均显著更高（P < 0.05 - 0.001）。
结果表明，在垂直跳跃中，受试者自身身体为产生最大机械输出提供了最佳负荷。如果未来对其他快速运动进行的研究结果得到证实，我们的发现可能支持这样的假设，即肌肉系统的设计目的是在仅承受自身身体重量和惯性负荷的情况下，在快速运动中产生最大机械输出。
