Higham Timothy E, Biewener Andrew A
Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC 29634, USA.
Proc Biol Sci. 2009 Mar 22;276(1659):1193-7. doi: 10.1098/rspb.2008.1734.
Muscle fatigue, a reduction in force as a consequence of exercise, is an important factor for any animal that moves, and can result from both peripheral and/or central mechanisms. Although much is known about whole-limb force generation and activation patterns in fatigued muscles under sustained isometric contractions, little is known about the in vivo dynamics of limb muscle function in relation to whole-body fatigue. Here we show that limb kinematics and contractile function in the lateral (LG) and medial (MG) gastrocnemius of helmeted guineafowl (Numida meleagris) are significantly altered following fatiguing exercise at 2ms-1 on an inclined treadmill. The two most significant findings were that the variation in muscle force generation, measured directly from the muscles' tendons, increased significantly with fatigue, and fascicle shortening in the proximal MG, but not the distal MG, decreased significantly with fatigue. We suggest that the former is a potential mechanism for decreased stability associated with fatigue. The region-specific alteration of fascicle behaviour within the MG as a result of fatigue suggests a complex response to fatigue that probably depends on muscle-aponeurosis and tendon architecture not previously explored. These findings highlight the importance of studying the integrative in vivo dynamics of muscle function in response to fatigue.
肌肉疲劳是运动导致的力量下降，对于任何运动的动物来说都是一个重要因素，它可能由外周和/或中枢机制引起。尽管在持续等长收缩下，关于疲劳肌肉中全肢力量产生和激活模式已经了解很多，但对于与全身疲劳相关的肢体肌肉功能的体内动态却知之甚少。在这里，我们表明，在倾斜跑步机上以2毫秒-1的速度进行疲劳运动后，盔珠鸡（Numida meleagris）外侧（LG）和内侧（MG）腓肠肌的肢体运动学和收缩功能会发生显著改变。两个最显著的发现是，直接从肌肉肌腱测量的肌肉力量产生变化随着疲劳显著增加，并且近端MG的肌束缩短，但远端MG没有，随着疲劳显著减少。我们认为前者是与疲劳相关的稳定性下降的潜在机制。由于疲劳导致MG内肌束行为的区域特异性改变，表明对疲劳的反应复杂，这可能取决于以前未探索过的肌肉-腱膜和肌腱结构。这些发现强调了研究肌肉功能在体内对疲劳反应的综合动态的重要性。
