Goldspink G
J Exp Biol. 1985 Mar;115:375-91. doi: 10.1242/jeb.115.1.375.
The various ways in which the power output of muscles can be changed are described. As a result of exercise and growth, force production is increased by an increase in the cross-sectional area of the fibres. This is associated with changes in the rate of synthesis and degradation of muscle proteins which lead to build up of the myofibrils. These then split longitudinally when they reach a critical size. This process is repeated so that the number of myofibrils increases very considerably. Also, during growth, the displacement is increased by increasing the length of the muscles. To do this more sarcomeres are produced in series along the length of the fibres. This is induced by stretch which also encourages fibre growth in girth as well as in length. Yet another way of changing the power output of a muscle is to change the types of muscle fibres (motor units) within the muscle. Fibre type transformation has been fibres (motor units) within the muscle. Fibre type transformation has been shown to occur with cross innervation and stimulation but it does not usually occur with exercise training. It has been possible, however, to change the fibre type proportions in young animals. Also, by combining stretch with stimulation, it has been possible for instance to make the fast glycolytic fibres add on fast oxidative type sarcomeres or even slow oxidation type sarcomeres. Interestingly, fibre transformation also occurs in some species of fish during acclimation to low temperatures in that the specific myofibrillar ATPase activity is increased. This means that the reduction in power output due to decreased temperature is to some extent compensated for by an increase in the intrinsic rate of shortening. EMG studies of fish swimming at different temperatures have shown that the acclimated fish can swim faster and can derive more aerobic sustainable power as a result of this change.
本文描述了肌肉输出功率可以改变的各种方式。由于运动和生长，通过增加纤维的横截面积，力量产生得以增强。这与肌肉蛋白质合成和降解速率的变化相关，这些变化导致肌原纤维的积累。当肌原纤维达到临界大小时，它们会纵向分裂。这个过程不断重复，使得肌原纤维的数量大幅增加。此外，在生长过程中，通过增加肌肉长度来增加位移。为此，沿着纤维长度方向会串联产生更多的肌节。这是由拉伸诱导的，拉伸还会促进纤维在周长和长度上的生长。改变肌肉输出功率的另一种方式是改变肌肉内的肌纤维类型（运动单位）。已证明纤维类型转化会伴随交叉神经支配和刺激而发生，但通常不会因运动训练而发生。然而，在幼小动物中改变纤维类型比例是可能的。而且，通过将拉伸与刺激相结合，例如有可能使快速糖酵解纤维增加快速氧化型肌节甚至慢氧化型肌节。有趣的是，在某些鱼类适应低温的过程中也会发生纤维转化，即特定肌原纤维ATP酶活性增加。这意味着由于温度降低导致的功率输出下降在一定程度上会通过缩短内在速率的增加得到补偿。对不同温度下游泳的鱼类进行的肌电图研究表明，经过适应的鱼类能够游得更快，并且由于这种变化能够获得更多的有氧可持续功率。
