Contractile properties of the shortening rat diaphragm in vitro.
Contractile properties of the shortening rat diaphragm in vitro.
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体外缩短大鼠膈肌的收缩特性。
DOI：
10.1152/jappl.1987.62.3.1111
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发表时间：
1987
影响因子：
3.3
通讯作者：
R. McCARTER
中科院分区：
文献类型：
--
作者：
I. Mardini;R. McCARTER
横隔性疲劳的定义是肌肉不能继续产生一定程度的张力。然而，适当缩短隔膜对于充分通风也同样重要。在本研究中，我们在体外研究了后负荷等张条件下大鼠横隔膜的收缩特性，以及疲劳对横隔膜收缩能力的影响。肌条的缩短取决于后负荷的大小、刺激的频率、刺激的持续时间和肌肉的初始长度。只有在较小的后载情况下，后加载的等张长度-张力关系才与长度与主动等长拉伸的关系相吻合。由等长或后负荷等长收缩引起的肌条疲劳与缩短程度的下降以及主动等长张力的下降有关。缩短能力和发展等长张力的能力并不是在所有条件下都有相同程度的下降。我们得出结论，肌肉疲劳会降低主动缩短和主动等长张力，这些特性的变化可能因实验条件的不同而不同。结果表明，横隔膜疲劳的定义应该扩大到包括肌肉适当缩短的能力。结果还表明，等长性能的测量可能不能提供疲劳横隔膜的整体性能的完整估计。
Diaphragmatic fatigue has been defined in terms of the failure of the muscle to continue to generate a given level of tension. Appropriate shortening of the diaphragm is, however, just as important for adequate ventilation. In this study we have examined in vitro the contractile properties of the rat diaphragm under afterloaded isotonic conditions and the effect of fatigue on the ability of the diaphragm to shorten. Shortening of the muscle strips was found to depend on size of afterload, frequency of stimulation, duration of stimulation, and initial length of the muscle. The afterloaded isotonic length-tension relationship coincided with the relationship between length and active isometric tension only for relatively small afterloads. Fatigue of the muscle strips, induced by isometric or afterloaded isotonic contractions, was associated with a decline in the extent of shortening as well as a decrease in active isometric tension. Ability to shorten and ability to develop isometric tension did not decrease to the same extent under all conditions. We conclude that active shortening, as well as active isometric tension, is decreased by muscular fatigue and that changes in these properties can be different depending on experimental conditions. The results suggest that the definition of diaphragmatic fatigue should be expanded to include the ability of the muscle to shorten by an appropriate amount. The results also suggest that measurement of isometric performance may not provide a complete estimate of the overall performance of the fatigued diaphragm.