de Haan A, van Doorn J E, Sargeant A J
Department of Exercise Physiology and Health Science, Faculty of Human Movement Sciences, Free University, Amsterdam, The Netherlands.
Pflugers Arch. 1988 Oct;412(6):665-7. doi: 10.1007/BF00583770.
Changes in isometric force, power output and relaxation rate have been measured during repetitive tetanic contractions in 2 groups of rats of different ages. During the first 5 contractions there were no differences between a young and mature group. In contrast to isometric force production, which decreased about 3% per contraction, power output initially increased to 108% of the power output in the first contraction. A greater reduction in power output and relaxation rate after the 5th contraction indicated a greater reduction of the cross-bridge cycling rate in the younger rats. ATP, phosphocreatine and lactate concentrations after the last contraction were not different between the age-groups. In contrast IMP production, which has been suggested may play a regulatory role during fatigue was twice as high in the young rats. Judged by isometric force production there is no age-related difference in fatiguability. However, profound differences were observed in power output, which indicates that quantification of fatigue as a loss of isometric force may be seriously misleading when considering the functional status of the muscle for normal dynamic contractions.
在两组不同年龄的大鼠进行重复性强直收缩期间，测量了等长力、功率输出和舒张速率的变化。在前5次收缩期间，年轻组和成熟组之间没有差异。与每次收缩等长力产生下降约3%相反，功率输出最初增加到第一次收缩时功率输出的108%。第5次收缩后功率输出和舒张速率的更大降低表明年轻大鼠中横桥循环速率的更大降低。最后一次收缩后，两组之间的ATP、磷酸肌酸和乳酸浓度没有差异。相比之下，有人认为可能在疲劳期间起调节作用的肌苷酸生成在年轻大鼠中是其两倍。从等长力产生来看，疲劳性没有年龄相关差异。然而，在功率输出方面观察到了显著差异，这表明在考虑肌肉进行正常动态收缩的功能状态时，将疲劳量化为等长力的丧失可能会产生严重误导。
