Johnson T P, Syme D A, Jayne B C, Lauder G V, Bennett A F
Department of Ecology and Evolutionary Biology, University of California, Irvine 92717.
Am J Physiol. 1994 Aug;267(2 Pt 2):R481-8. doi: 10.1152/ajpregu.1994.267.2.R481.
We recorded electromyograms of slow-twitch (red) muscle fibers and videotaped swimming in the largemouth bass (Micropterus salmoides) during cruise, burst-and-glide, and C-start maneuvers. By use of in vivo patterns of stimulation and estimates of strain, in vitro power output was measured at 20 degrees C with the oscillatory work loop technique on slow-twitch fiber bundles from the midbody area near the soft dorsal fin. Power output increased slightly with cycle frequency to a plateau of approximately 10 W/kg at 3-5 Hz, encompassing the normal range of tail-beat frequencies for steady swimming (approximately 2-4 Hz). Power output declined at cycle frequencies simulating unsteady swimming (burst-and-glide, 10 Hz; C-start, 15 Hz). However, activating the muscle at 10 Hz did significantly increase the net work done compared with the work produced by the inactive muscle (work done by the viscous and elastic components). Thus this study provides further insight into the apparently paradoxical observation that red muscle can contribute little or no power and yet continues to show some recruitment during unsteady swimming. Comparison with published values of power requirements from oxygen consumption measurements indicates a limit to steady swimming speed imposed by the maximum power available from red muscle.
我们记录了大口黑鲈（Micropterus salmoides）在巡航、爆发式滑行和C型启动动作过程中慢肌（红色）纤维的肌电图，并对其游泳过程进行了录像。利用体内刺激模式和应变估计值，在20摄氏度下，采用振荡功循环技术，对靠近软背鳍的中体区域的慢肌纤维束进行体外功率输出测量。功率输出随循环频率略有增加，在3 - 5赫兹时达到约10瓦/千克的平台期，涵盖了稳定游泳时尾鳍摆动频率的正常范围（约2 - 4赫兹）。在模拟非稳定游泳的循环频率下（爆发式滑行，10赫兹；C型启动，15赫兹），功率输出下降。然而，与非活动肌肉产生的功（粘性和弹性成分所做的功）相比，以10赫兹激活肌肉确实显著增加了所做的净功。因此，本研究进一步深入了解了这一明显矛盾的观察结果：红色肌肉在非稳定游泳过程中贡献很小或不贡献功率，但仍会持续表现出一定程度的募集。与通过耗氧量测量得出的功率需求的已发表值进行比较，表明红色肌肉可提供的最大功率对稳定游泳速度存在限制。
