de Haan A, Jones D A, Sargeant A J
Department of Exercise Physiology and Health Science, Faculty of Human Movement Sciences, Free University, Amsterdam, The Netherlands.
Pflugers Arch. 1989 Feb;413(4):422-8. doi: 10.1007/BF00584493.
The force-velocity characteristics of rat medial gastrocnemius muscle have been determined by measuring the force sustained during constant velocity releases of the muscle stimulated in situ at an ambient temperature of 26 degrees C. The velocity of unloaded shortening was determined using the "slack" test and rate of relaxation from the half time of force loss at the end of stimulation. Measurements were first made on fresh muscles using short contractions and then during a series which consisted of a 15 s contraction (fatigued muscle), followed by 15 min recovery and a 1 s contraction (recovered muscle). After a 5 min recovery period the sequence was repeated. Comparison was made between the fatigued and recovered state in each preparation in order to allow for any change in the preparation during the course of the experiment. After 15 s contraction the fatigued muscles showed a marked reduction in all parameters measured. In fatigued muscles the isometric force fell to 48 +/- 15% (mean +/- SD) and there was a decrease in maximum velocity of shortening to 66%. These changes in the force-velocity relationship were accompanied by slowing of relaxation so that the half time of relaxation nearly doubled. The consequence of these changes was that the maximum power output was reduced by a much greater extent than was the isometric force (75% vs. 52%). It is suggested that the changes in force-velocity characteristics reflect a reduction in cross-bridge cycling in fatigued muscle.
通过测量在26摄氏度环境温度下原位刺激的大鼠腓肠肌在恒速释放过程中维持的力，确定了其力-速度特性。使用“松弛”试验确定无负荷缩短速度，并根据刺激结束时力损失的半衰期确定松弛速率。首先对新鲜肌肉进行短时间收缩测量，然后在一系列测量中，先进行15秒收缩（疲劳肌肉），接着15分钟恢复，再进行1秒收缩（恢复肌肉）。经过5分钟恢复期后，重复该序列。对每个标本的疲劳状态和恢复状态进行比较，以考虑实验过程中标本的任何变化。15秒收缩后，疲劳肌肉在所有测量参数上均出现显著降低。在疲劳肌肉中，等长力降至48±15%（平均值±标准差），最大缩短速度降低至66%。力-速度关系的这些变化伴随着松弛减慢，使得松弛半衰期几乎翻倍。这些变化的结果是，最大功率输出的降低幅度远大于等长力（分别为75%和52%）。有人认为，力-速度特性的变化反映了疲劳肌肉中横桥循环的减少。
