Meyers Ron A, McFarland Joshua C
Department of Zoology, Weber State University, Ogden UT 84408-2505 USA.
Acta Zool. 2016 Jul;97(3):319-324. doi: 10.1111/azo.12125. Epub 2015 Mar 17.
Slow fibers are typically characterized as functioning in avian postural behaviors such as soaring flight, and are described for a number of elite soarers such as vultures, pelicans and albatrosses. Golden Eagles and Bald Eagles also display soaring behavior and we examined their flight muscles for the presence of slow fibers. Surprisingly, eagles lack a deep layer to the pectoralis found in other soaring species. Additionally, the pectoralis as well as other shoulder muscles had few to no slow muscle fibers. The lack of functionally meaningful numbers of slow muscle fibers in eagle flight muscles indicates that they must rely on fast fibers for posture; these can function in that role due to their high aerobic capacity and also perhaps a "tuning" of muscle contraction frequency to function more efficiently at isometric contractions.
慢肌纤维通常被认为在鸟类的姿势行为中发挥作用，比如翱翔飞行，并且在一些擅长翱翔的鸟类如秃鹫、鹈鹕和信天翁身上有所描述。金雕和白头海雕也表现出翱翔行为，我们检查了它们的飞行肌肉中慢肌纤维的存在情况。令人惊讶的是，鹰类的胸肌缺乏其他翱翔物种所具有的深层结构。此外，胸肌以及其他肩部肌肉几乎没有或根本没有慢肌纤维。鹰类飞行肌肉中缺乏具有功能意义数量的慢肌纤维表明，它们在保持姿势时必须依赖快肌纤维；由于快肌纤维具有较高的有氧能力，并且可能通过对肌肉收缩频率进行“调节”，从而在等长收缩时更有效地发挥作用，所以能够起到这个作用。
