Department of Ecology and Evolutionary Biology, Brown University , Providence, Rhode Island.
J Appl Physiol (1985). 2019 Mar 1;126(3):593-598. doi: 10.1152/japplphysiol.00330.2018. Epub 2018 Dec 13.
Most limb muscles operate within a compartment defined by fascial layers that enclose a muscle or groups of muscles within a defined space. These compartments are important clinically, because fluid accumulation can cause ischemia and tissue necrosis if untreated. Little is known, however, about how fascial enclosures influence healthy muscle function. One previous study showed that removing a fascial covering reduced the force output of a muscle under maximal stimulation. We hypothesized that such reduction in force output was due to a change in the muscle length following fasciotomy and that a reduced force output could be explained by the length-tension relationship of muscle. Thus we predicted that the maximum force across a range of lengths would be unchanged following fasciotomy. We measured maximal tetanic force output in a wing muscle in wild turkeys both before and after removal of fascia that enclosed the muscle in a compartment. Our hypothesis was not supported. The length-tension curve of this muscle showed that removal of fascia reduced maximum force output to 72 ± 10% of the prefascial release condition. Thus a reduction in muscle force following fasciotomy was not explained by a change in muscle length. The mechanism underlying reduction in force is unclear, but it suggests that the assumption underlying most isolated muscle experiments, i.e., removal of a muscle from its situation in vivo does not influence its maximal mechanical output, may need reexamining. NEW & NOTEWORTHY Most limb muscles are enclosed within compartments bound by robust fascial sheets. The mechanical significance of the close packing of muscle and fascia is largely unexplored. We used an animal model to show that removal of a fascial covering reduces the maximal force developed during contraction. These results raise questions about the use of isolated muscles to estimate muscle performance and suggest that a muscle's mechanical surrounding influences performance by mechanisms that are not understood.
大多数肢体肌肉在由筋膜层定义的隔室内运作，这些筋膜层将肌肉或肌肉群封闭在一个特定的空间内。这些隔室在临床上很重要，因为如果不治疗，液体积聚会导致缺血和组织坏死。然而，人们对筋膜封闭如何影响健康肌肉功能知之甚少。之前的一项研究表明，去除筋膜覆盖物会降低最大刺激下肌肉的力输出。我们假设这种力输出的减少是由于筋膜切开术后肌肉长度的变化引起的，而力输出的减少可以用肌肉的长度-张力关系来解释。因此，我们预测筋膜切开术后，肌肉在一系列长度下的最大力将保持不变。我们测量了野生火鸡翅膀肌肉在去除包裹肌肉的筋膜前后的最大强直力输出。我们的假设没有得到支持。该肌肉的长度-张力曲线表明，去除筋膜会将最大力输出降低到筋膜释放前条件的 72±10%。因此，筋膜切开术后肌肉力的减少不能用肌肉长度的变化来解释。力减少的机制尚不清楚，但它表明，大多数离体肌肉实验的假设，即从体内环境中取出肌肉不会影响其最大机械输出，可能需要重新考虑。新的和值得注意的是：大多数肢体肌肉都被包裹在由坚固的筋膜片组成的隔室内。肌肉和筋膜紧密包装的机械意义在很大程度上尚未得到探索。我们使用动物模型表明，去除筋膜覆盖物会降低收缩过程中产生的最大力。这些结果引发了关于使用离体肌肉来估计肌肉性能的问题，并表明肌肉的机械环境通过尚未理解的机制影响性能。
