Lodder M A, de Haan A, Sargeant A J
Department of Muscle and Exercise Physiology, Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
Eur J Appl Physiol Occup Physiol. 1994;69(5):429-34. doi: 10.1007/BF00865407.
The effect of growth on work output, energy consumption and efficiency during repetitive dynamic contractions was determined using extensor digitorum longus muscles of 40-, 60-, 120- and 700-day-old male Wistar rats. When work output of each contraction was normalized to the work output of the first contraction it was found that work output initially increased over the first 10-20 contractions by approximately 8% in each age group. Thereafter a faster decrease in work output was found in the youngest group (approximately 2% each contraction) compared to the older groups (approximately 0.7% each contraction). After 40 contractions the reduction in work output was significantly different only between the youngest group and the two oldest groups (-30% vs -5%). These differences in fatigue were not associated with differences in adenosine 5'-triphosphate and phosphocreatine concentrations or in lactate production. Total work output and high-energy phosphate consumption increased by approximately 555% and 380% from age 40 to 120 days, respectively. Consequently, efficiency was significantly higher (approximately 32%) in the older groups compared to 40-day-old animals. Normalized for muscle mass, mean rate of high-energy phosphate consumption was similar in all groups whereas mean power output was significantly lower in the youngest group (approximately 46%). Thus, the difference in efficiency between the young and the other groups may be attributed to a lower external power production in the youngest group rather than changes in energy turnover.
利用40日龄、60日龄、120日龄和700日龄雄性Wistar大鼠的趾长伸肌，测定了重复动态收缩过程中生长对工作输出、能量消耗和效率的影响。当将每次收缩的工作输出标准化为第一次收缩的工作输出时，发现每个年龄组在最初的10 - 20次收缩中工作输出最初增加了约8%。此后，最年轻的组工作输出下降更快（每次收缩约2%），而较年长的组（每次收缩约0.7%）下降较慢。40次收缩后，仅最年轻的组与两个最年长的组之间工作输出的降低存在显著差异（-30%对-5%）。这些疲劳差异与三磷酸腺苷、磷酸肌酸浓度或乳酸生成的差异无关。从40日龄到120日龄，总工作输出和高能磷酸消耗分别增加了约555%和380%。因此，与40日龄的动物相比，较年长的组效率显著更高（约32%）。以肌肉质量进行标准化后，所有组的高能磷酸消耗平均速率相似，而最年轻组的平均功率输出显著更低（约46%）。因此，年轻组与其他组之间效率的差异可能归因于最年轻组较低的外部功率产生，而非能量转换的变化。
