Zajac F E, Zomlefer M R, Levine W S
J Exp Biol. 1981 Apr;91:73-86. doi: 10.1242/jeb.91.1.73.
Cats were trained to jump from a force platform to their maximum achievable heights. Vertical ground reaction forces developed by individual hindlimbs showed that the propulsion phase consists of two epochs. During the initial "preparatory phase' the cat can traverse many different paths. Irrespective of the path traversed, however, the cat always attains the same position, velocity and momentum at the end of this phase. Starting from this dynamic state the cat during the subsequent "launching phase' (about 150 ms long) generates significant propulsion as its hindlimbs develop force with identical, stereotypic profiles. Cinematographic data, electromyographic data, and computed torques about the hip, knee and ankle joints indicate that during the jump proximal extensor musculature is activated before distal musculature. During terminal experiments when the hindlimb was set at positions corresponding to those in the jump, isometric torques produced by tetanic stimulation of groups of extensor and flexor muscles were compared with computed torques developed by the same cat during previous jumps. These comparisons suggest that extensor muscles of the hindlimb are fully activated during the maximal vertical jump.
猫被训练从一个测力平台跳到它们能够达到的最大高度。单个后肢产生的垂直地面反作用力表明，推进阶段由两个时期组成。在最初的“准备阶段”，猫可以通过许多不同的路径。然而，无论所经过的路径如何，猫在这个阶段结束时总是达到相同的位置、速度和动量。从这个动态状态开始，猫在随后的“发射阶段”（约150毫秒长）产生显著的推进力，因为其后肢以相同的、刻板的模式发力。电影数据、肌电图数据以及髋关节、膝关节和踝关节的计算扭矩表明，在跳跃过程中，近端伸肌比远端肌肉更早被激活。在最终实验中，当后肢被设置在与跳跃中相应的位置时，将伸肌和屈肌组的强直刺激产生的等长扭矩与同一只猫在之前跳跃中产生的计算扭矩进行比较。这些比较表明，后肢伸肌在最大垂直跳跃过程中被充分激活。
