Kinesiology and Physical Education, McGill University, Montreal, QC, Canada.
Sci Rep. 2020 Dec 9;10(1):21590. doi: 10.1038/s41598-020-78457-1.
When a muscle is stretched during a contraction, the resulting steady-state force is higher than the isometric force produced at a comparable sarcomere length. This phenomenon, also referred to as residual force enhancement, cannot be readily explained by the force-sarcomere length relation. One of the most accepted mechanisms for the residual force enhancement is the development of sarcomere length non-uniformities after an active stretch. The aim of this study was to directly investigate the effect of non-uniformities on the force-producing capabilities of isolated myofibrils after they are actively stretched. We evaluated the effect of depleting a single A-band on sarcomere length non-uniformity and residual force enhancement. We observed that sarcomere length non-uniformity was effectively increased following A-band depletion. Furthermore, isometric forces decreased, while the percent residual force enhancement increased compared to intact myofibrils (5% vs. 20%). We conclude that sarcomere length non-uniformities are partially responsible for the enhanced force production after stretch.
当肌肉在收缩过程中被拉伸时，产生的稳定状态力高于在可比肌节长度下产生的等长力。这种现象也称为剩余力增强，不能用力-肌节长度关系来轻易解释。剩余力增强的最被接受的机制之一是在主动拉伸后肌节长度的非均匀性的发展。本研究的目的是直接研究肌节长度非均匀性对主动拉伸后的分离肌原纤维产生力的能力的影响。我们评估了耗尽单个 A 带对肌节长度非均匀性和剩余力增强的影响。我们观察到，耗尽 A 带后肌节长度非均匀性显著增加。此外，与完整的肌原纤维相比，等长力降低，而剩余力增强的百分比增加（5%比 20%）。我们的结论是，肌节长度非均匀性部分解释了拉伸后力增强的原因。
