Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, Ontario, Canada.
Department of Biomedical Sciences, Neuromuscular Physiology Laboratory, University of Padua, Padua, Italy.
J Appl Physiol (1985). 2022 Jul 1;133(1):87-103. doi: 10.1152/japplphysiol.00114.2022. Epub 2022 May 19.
Skeletal muscle has the remarkable ability to remodel and adapt, such as the increase in serial sarcomere number (SSN) or fascicle length (FL) observed after overstretching a muscle. This type of remodeling is termed longitudinal muscle fascicle growth, and its impact on biomechanical function has been of interest since the 1960s due to its clinical applications in muscle strain injury, muscle spasticity, and sarcopenia. Despite simplified hypotheses on how longitudinal muscle fascicle growth might influence mechanical function, existing literature presents conflicting results partly due to a breadth of methodologies. The purpose of this review is to outline what is currently known about the influence of longitudinal muscle fascicle growth on mechanical function and suggest future directions to address current knowledge gaps and methodological limitations. Various interventions indicate longitudinal muscle fascicle growth can increase the optimal muscle length for active force, but whether the whole force-length relationship widens has been less investigated. Future research should also explore the ability for longitudinal fascicle growth to broaden the torque-angle relationship's plateau region, and the relation to increased force during shortening. Without a concurrent increase in intramuscular collagen, longitudinal muscle fascicle growth also reduces passive tension at long muscle lengths; further research is required to understand whether this translates to increased joint range of motion. Finally, some evidence suggests longitudinal fascicle growth can increase maximum shortening velocity and peak isotonic power; however, there has yet to be direct assessment of these measures in a neurologically intact model of longitudinal muscle fascicle growth.
骨骼肌具有显著的重塑和适应能力，例如在过度拉伸肌肉后观察到的串联肌节数量（SSN）或肌束长度（FL）增加。这种重塑类型被称为纵向肌束生长，由于其在肌肉拉伤、肌肉痉挛和肌肉减少症中的临床应用，自 20 世纪 60 年代以来，其对生物力学功能的影响一直引起人们的兴趣。尽管关于纵向肌束生长如何影响机械功能的简化假说，但由于方法的多样性，现有的文献结果存在矛盾。本综述的目的是概述目前关于纵向肌束生长对机械功能影响的认识，并提出未来的研究方向，以解决当前的知识差距和方法学限制。各种干预表明，纵向肌束生长可以增加主动力的最佳肌肉长度，但整个力-长度关系是否变宽的研究较少。未来的研究还应探讨纵向束生长扩大扭矩-角度关系平台区的能力，以及与缩短过程中力增加的关系。如果没有肌内胶原的同时增加，纵向肌束生长也会降低长肌肉长度的被动张力；需要进一步研究以了解这是否转化为关节运动范围的增加。最后，有证据表明纵向束生长可以增加最大缩短速度和峰值等张功率；然而，在纵向肌束生长的神经完整模型中，尚未直接评估这些措施。
