McCully K K, Faulkner J A
J Appl Physiol (1985). 1986 Jul;61(1):293-9. doi: 10.1152/jappl.1986.61.1.293.
Lengthening (eccentric) contractions result in injury to skeletal muscle fibers. Two hypotheses were tested through lengthening contractions of an in situ muscle preparation: the extent of injury increases with increases in the duration; and the extent of injury increases with increases in the peak force. Mice were anesthetized, and distal tendons of the extensor digitorum longus muscles were attached to a servomotor. Muscles were stimulated at 150 Hz and lengthened 20% of fiber length (Lf). Lengthening contractions were performed at 0.2, 0.5, or 1.0 Lf/s with durations of 0.5-15 min. Peak force during lengthening contractions at 1.0 Lf/s was decreased by inducing fatigue with isometric contractions, stimulating at 70-100 Hz, or 3) lengthening 10% of Lf. Injury was assessed 3 days after lengthening contractions by histological appearance and maximum force (Po) development. Injury increased with duration up to 5 min. After 5 min, fatigue appeared to prevent further injury. Results for 0.2 and 0.5 Lf/s were similar to those for 1.0 Lf/s but with less injury. A high correlation was observed between histological appearance of injury and the decrease in Po. The extent of injury was related to the peak force developed during the lengthening contractions.
拉长（离心）收缩会导致骨骼肌纤维损伤。通过对原位肌肉标本进行拉长收缩来检验两个假说：损伤程度随持续时间的增加而增加；损伤程度随峰值力的增加而增加。将小鼠麻醉，然后把趾长伸肌的远端肌腱连接到一个伺服电机上。以150Hz的频率刺激肌肉，并使其长度拉长纤维长度（Lf）的20%。以0.2、0.5或1.0 Lf/s的速度进行拉长收缩，持续时间为0.5 - 15分钟。通过等长收缩诱导疲劳、以70 - 100Hz的频率刺激或拉长Lf的10%，来降低1.0 Lf/s时拉长收缩期间的峰值力。在拉长收缩3天后，通过组织学外观和最大力（Po）的产生来评估损伤情况。损伤程度在持续时间长达5分钟时会增加。5分钟后，疲劳似乎会阻止进一步的损伤。0.2和0.5 Lf/s时的结果与1.0 Lf/s时相似，但损伤较小。在损伤的组织学外观与Po的降低之间观察到高度相关性。损伤程度与拉长收缩期间产生的峰值力有关。
