Cecchi G, Colomo F, Lombardi V, Piazzesi G
Pflugers Arch. 1987 Jun;409(1-2):39-46. doi: 10.1007/BF00584747.
Stiffness measurements were performed during the rise, the plateau and the relaxation of tetanic contractions both in whole single muscle fibres and in tendon-free fibre segments under either fixed-end or length-clamp conditions. Fibres were isolated from the tibialis anterior muscle of the frog. Experiments were performed at 2-6 degrees C. Changes in length of tendon-free fibre segments were monitored by means of a "striation follower", an opto-electronic device which, during contraction, measured sarcomere displacement at the level of two selected regions of a fibre. Fast length perturbations imposed at one tendon end of a fibre during the plateau of tetanic contractions distribute uniformly along its length. During the tetanus rise stiffness led isometric tension in whole fibres under fixed conditions as well as in tendon-free fibre segments under length-clamp conditions. It was confirmed that a significant part of the unlinearity of T1 relations is determined by tendon compliance. During the isometric phase of relaxation in fixed-end tetani, the decline of tension led that of stiffness both in whole fibres and in tendon-free fibre segments. It is concluded that the shift observed between stiffness and tension during tetanus rise and relaxation represents a true specific event in the contractile process.
在强直收缩的上升期、平台期和松弛期，分别在固定端或长度钳制条件下，对完整的单根肌纤维以及无腱纤维段进行了僵硬度测量。纤维取自青蛙的胫前肌。实验在2至6摄氏度下进行。无腱纤维段的长度变化通过“条纹跟踪器”进行监测，这是一种光电装置，在收缩过程中，可测量纤维两个选定区域水平处的肌节位移。在强直收缩平台期，在纤维的一个腱端施加的快速长度扰动会沿其长度均匀分布。在强直收缩上升期，在固定条件下的完整纤维以及长度钳制条件下的无腱纤维段中，僵硬度变化领先于等长张力变化。已证实，T1关系的显著非线性部分是由腱的顺应性决定的。在固定端强直收缩的等长松弛阶段，无论是完整纤维还是无腱纤维段，张力的下降都领先于僵硬度的下降。得出的结论是，在强直收缩上升期和松弛期观察到的僵硬度和张力之间的变化代表了收缩过程中一个真正的特定事件。
