Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
Muscle Nerve. 2011 Sep;44(3):410-7. doi: 10.1002/mus.22073.
Fatigue disrupts muscle force summation and is associated with a decrease in cytoplasmic Ca(2+) concentration. The purpose of this study was to compare summation during fatigue and recovery with summation during dantrolene-induced inhibition of Ca(2+) release.
Rat medial gastrocnemius muscles were evaluated before and after fatigue, or during exposure to dantrolene. Summation was quantified by the ratio of the force transient associated with the final activation in a train of stimuli (Twf), obtained by subtraction of the force with one less stimulus, and the force of the twitch (Tw).
This ratio (Twf/Tw) decreased from 2.46 ± 0.11 (mean ± SEM) to 0.8 ± 0.1 during intermittent contractions, but was still significantly different from non-fatigued muscle after 10 min of recovery. Dantrolene altered summation, as Twf/Tw was 1.7 ± 0.2 and 1.27 ± 0.15 at a low dose and a high dose, respectively.
Inhibition of Ca(2+) release alters summation, but repetitive stimulation leading to fatigue changes it more substantially.
疲劳会破坏肌肉力量的总和，并与细胞质钙离子浓度的降低有关。本研究的目的是比较疲劳和恢复期间的总和与钙释放抑制的丹曲洛林期间的总和。
在疲劳之前和之后，或在丹曲洛林暴露期间，评估大鼠内侧腓肠肌。总和通过在刺激的一连串中最后一次激活相关的力瞬变（Twf）的比率来量化，通过减去一个刺激的力来获得，并且与抽搐力（Tw）。
该比率（Twf / Tw）从 2.46 ± 0.11（平均值±SEM）降低到 0.8 ± 0.1，在间歇性收缩期间，但在恢复 10 分钟后仍明显不同于非疲劳肌肉。丹曲洛林改变了总和，因为 Twf / Tw 分别为 1.7 ± 0.2 和 1.27 ± 0.15，低剂量和高剂量。
钙释放抑制改变了总和，但导致疲劳的重复刺激改变了更多。
