Influence of residual force enhancement and elongation of attached cross-bridges on stretch-shortening cycle in skinned muscle fibers.
Influence of residual force enhancement and elongation of attached cross-bridges on stretch-shortening cycle in skinned muscle fibers.
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DOI：
10.14814/phy2.13477
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发表时间：
2017-11
影响因子：
2.5
通讯作者：
Herzog W
中科院分区：
文献类型：
--
作者：
Fukutani A;Joumaa V;Herzog W
在拉伸缩短周期（SSC）期间增加的肌肉力量已被广泛研究。然而，导致SSC中肌肉力量增加的机制仍然未知。本研究的目的是确定残余力增强和附加横桥伸长对SSC工作增强的影响。在对照组中，去皮的兔比目鱼肌纤维被动地从平均肌节长度2.4 μm延长到3.0 μm，激活后主动缩短到2.4 μm。对于过渡条件，纤维从平均肌节长度2.4 μ m主动伸长至3.0 μm。主动延长结束后2s，纤维主动缩短至2.4 μm。在SSC条件下，肌节平均长度从2.4 μ m主动延长到3.0 μm，然后立即主动缩短到2.4 μm。通过与纯粹主动缩短收缩期间测量的机械功相比，主动缩短期间机械功的增加来量化SSC中增加的肌肉力量。工作增强是显着更大的SSC相比，过渡条件。这种差异与过渡测试中主动延长和缩短阶段之间的暂停有关，这可能导致主动拉伸引起的连接横桥的平均伸长率降低。由于在过渡条件下仍然观察到一些功增强，因此另一个因素，例如拉伸引起的残余力增强，也一定有助于SSC中的功增强。
Increased muscle force during stretch‐shortening cycles (SSCs) has been widely examined. However, the mechanisms causing increased muscle force in SSCs remain unknown. The purpose of this study was to determine the influence of residual force enhancement and elongation of attached cross‐bridges on the work enhancement in SSCs. For the Control condition, skinned rabbit soleus fibers were elongated passively from an average sarcomere length of 2.4 to 3.0 μm, activated and then actively shortened to 2.4 μm. For the Transition condition, fibers were elongated actively from an average sarcomere length of 2.4 to 3.0 μm. Two seconds after the end of active lengthening, fibers were actively shortened to 2.4 μm. In the SSC condition, fibers were lengthened actively from an average sarcomere length of 2.4 to 3.0 μm, and then immediately shortened actively to 2.4 μm. Increased muscle force in the SSCs was quantified by the increase in mechanical work during active shortening compared to the mechanical work measured during the purely active shortening contractions. Work enhancement was significantly greater in the SSC compared to the Transition conditions. This difference was associated with the pause given between the active lengthening and shortening phase in the Transition test, which likely resulted in a reduction of the average elongation of the attached cross‐bridges caused by active stretching. Since some work enhancement was still observed in the Transition condition, another factor, for example the stretch‐induced residual force enhancement, must also have contributed to the work enhancement in SSCs.