Ward C W, Spangenburg E E, Diss L M, Williams J H
Muscular Function Laboratory, Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
Am J Physiol. 1998 Jul;275(1):R99-R104. doi: 10.1152/ajpregu.1998.275.1.R99.
The purpose of this investigation was to examine changes in sarcoplasmic reticulum (SR) function in muscles subjected to different patterns of muscle activity. Frog sartorius muscles were stimulated with tetanic trains (100 ms, 100 Hz) delivered at rates of 2.0, 0.5, and 0.2 trains/s. In one set of experiments, stimulation was continued until force had declined to approximately 17% of initial (constant fatigue), whereas in the other set, stimulation was continued for 1 min (constant duration). In the constant-fatigue experiments, Ca2+ uptake (1 mM MgATP) and release rates (25 microM AgNO3, 5 mM 4-chloro-m-cresol) were depressed by similar extents following each protocol. This occurred despite 1, 4, and 17 min of stimulation, respectively, used to induce fatigue. In the constant-duration experiments, larger reductions in SR function occurred following the highest frequency stimulation protocol. These data suggest that when muscles are fatigued to similar extents, depressions in SR function are independent of the activity protocol. On the other hand, when a constant duration of activity is imposed, changes in SR function are closely linked to the extent of force reduction.
本研究的目的是检测不同肌肉活动模式下肌肉肌浆网（SR）功能的变化。以2.0、0.5和0.2次/秒的频率，用强直刺激串（100毫秒，100赫兹）刺激青蛙缝匠肌。在一组实验中，持续刺激直至力量下降至初始值的约17%（持续疲劳），而在另一组实验中，持续刺激1分钟（持续时间恒定）。在持续疲劳实验中，每种方案后钙摄取（1毫摩尔镁三磷酸腺苷）和释放速率（25微摩尔硝酸银，5毫摩尔4-氯间甲酚）均受到相似程度的抑制。尽管分别使用1、4和17分钟的刺激来诱导疲劳，但这种情况仍会发生。在持续时间恒定的实验中，最高频率刺激方案后肌浆网功能的降低幅度更大。这些数据表明，当肌肉疲劳程度相似时，肌浆网功能的降低与活动方案无关。另一方面，当施加恒定的活动持续时间时，肌浆网功能的变化与力量降低的程度密切相关。
