Work and power output in the hindlimb muscles of Cuban tree frogs Osteopilus septentrionalis during jumping.
Work and power output in the hindlimb muscles of Cuban tree frogs Osteopilus septentrionalis during jumping.
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发表时间：
1997-11
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通讯作者：
M. M. Peplowski-M.;Richard L. Marsh
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作者：
M. M. Peplowski-M.;Richard L. Marsh
有人提出，在跳跃的起飞阶段，小青蛙使用弹射机制来放大肌肉力量的产生。这一结论是基于后肢肌肉提供的力量和起飞过程中所需力量之间的明显差异。本研究提供了支持这一结论的肌肉收缩特性、形态和跳跃性能的综合数据。我们在这里表明，古巴树蛙在起飞过程中预测的功率输出至少是肌肉输出的七倍。我们认为缝匠肌代表了这些动物的大部分后肢肌肉，因为这块肌肉具有小青蛙其他后肢肌肉的典型特征。在25℃时，这块肌肉的最大缩短速度(Vmax)为8.77+/-0.62L0 S-1(其中L0是产生最大等长力的肌肉长度)，最大等长力(P0)为24.1+/-2.3N cm-2，最大等张功率输出为230+/-9.2W kg-1肌肉(平均值为+/-S.E.M.)。相比之下，在测量的最长跳跃(约1.4米)中，加速动物所需的功率超过整个后肢肌肉的800W kg-1。预计峰值瞬时功率是该值的两倍。这些估计可能是保守的，因为可能推动跳跃的肌肉只占后肢总肌肉质量的85%。肌肉需要的总机械功很高(高达60J kg-1)，但在脊椎动物骨骼肌预测的功的范围内。显然，这项工作的很大一部分必须在起飞前完成和储存，以解决跳跃过程中的高功率输出。有趣的是，跳跃过程中的肌肉功输出与温度有关，温度越高，产生的功越大。功的热依赖不是来自简单的肌肉特性，而是必须反映在跳跃推进阶段这些特性与骨骼肌系统的其他组成部分之间的相互作用。
It has been suggested that small frogs use a catapult mechanism to amplify muscle power production during the takeoff phase of jumping. This conclusion was based on an apparent discrepancy between the power available from the hindlimb muscles and that required during takeoff. The present study provides integrated data on muscle contractile properties, morphology and jumping performance that support this conclusion. We show here that the predicted power output during takeoff in Cuban tree frogs Osteopilus septentrionalis exceeds that available from the muscles by at least sevenfold. We consider the sartorius muscle as representative of the bulk of the hindlimb muscles of these animals, because this muscle has properties typical of other hindlimb muscles of small frogs. At 25 degrees C, this muscle has a maximum shortening velocity (Vmax) of 8.77 +/- 0.62 L0 s-1 (where L0 is the muscle length yielding maximum isometric force), a maximum isometric force (P0) of 24.1 +/- 2.3 N cm-2 and a maximum isotonic power output of 230 +/- 9.2 W kg-1 of muscle (mean +/- S.E.M.). In contrast, the power required to accelerate the animal in the longest jumps measured (approximately 1.4 m) is more than 800 W kg-1 of total hindlimb muscle. The peak instantaneous power is expected to be twice this value. These estimates are probably conservative because the muscles that probably power jumping make up only 85% of the total hindlimb muscle mass. The total mechanical work required of the muscles is high (up to 60 J kg-1), but is within the work capacities predicted for vertebrate skeletal muscle. Clearly, a substantial portion of this work must be performed and stored prior to takeoff to account for the high power output during jumping. Interestingly, muscle work output during jumping is temperature-dependent, with greater work being produced at higher temperatures. The thermal dependence of work does not follow from simple muscle properties and instead must reflect the interaction between these properties and the other components of the skeletomuscular system during the propulsive phase of the jump.