Maganaris Constantinos N, Chatzistergos Panagiotis, Reeves Neil D, Narici Marco V
School of Sport and Exercise Sciences, Liverpool John Moores University Liverpool, UK.
Faculty of Health Sciences, Staffordshire University Stoke-on-Trent, UK.
Front Physiol. 2017 Feb 28;8:91. doi: 10.3389/fphys.2017.00091. eCollection 2017.
By virtue of their anatomical location between muscles and bones, tendons make it possible to transform contractile force to joint rotation and locomotion. However, tendons do not behave as rigid links, but exhibit viscoelastic tensile properties, thereby affecting the length and contractile force in the in-series muscle, but also storing and releasing elastic stain energy as some tendons are stretched and recoiled in a cyclic manner during locomotion. In the late 90s, advancements were made in the application of ultrasound scanning that allowed quantifying the tensile deformability and mechanical properties of human tendons . Since then, the main principles of the ultrasound-based method have been applied by numerous research groups throughout the world and showed that tendons increase their tensile stiffness in response to exercise training and chronic mechanical loading, in general, by increasing their size and improving their intrinsic material. It is often assumed that these changes occur homogenously, in the entire body of the tendon, but recent findings indicate that the adaptations may in fact take place in some but not all tendon regions. The present review focuses on these regional adaptability features and highlights two paradigms where they are particularly evident: (a) Chronic mechanical loading in healthy tendons, and (b) tendinopathy. In the former loading paradigm, local tendon adaptations indicate that certain regions may "see," and therefore adapt to, increased levels of stress. In the latter paradigm, local pathological features indicate that certain tendon regions may be "stress-shielded" and degenerate over time. Eccentric exercise protocols have successfully been used in the management of tendinopathy, without much sound understanding of the mechanisms underpinning their effectiveness. For insertional tendinopathy, in particular, it is possible that the effectiveness of a loading/rehabilitation protocol depends on the topography of the stress created by the exercise and is not only reliant upon the type of muscle contraction performed. To better understand the micromechanical behavior and regional adaptability/mal-adaptability of tendon tissue it is important to estimate its internal stress-strain fields. Recent relevant advancements in numerical techniques related to tendon loading are discussed.
由于肌腱位于肌肉和骨骼之间的解剖位置，它能够将收缩力转化为关节旋转和运动。然而，肌腱并非刚性连接，而是表现出粘弹性拉伸特性，这不仅会影响串联肌肉中的长度和收缩力，还会在运动过程中，当一些肌腱以循环方式伸展和回缩时，储存和释放弹性应变能。在20世纪90年代后期，超声扫描技术取得了进展，能够量化人类肌腱的拉伸变形能力和力学性能。从那时起，基于超声的方法的主要原理已被世界各地的众多研究团队应用，并表明肌腱通常通过增加其尺寸和改善其内在材料来响应运动训练和慢性机械负荷，从而提高其拉伸刚度。人们通常认为这些变化在肌腱的整个主体中均匀发生，但最近的研究结果表明，这些适应性变化实际上可能只发生在部分而非全部肌腱区域。本综述聚焦于这些区域适应性特征，并突出了两个特别明显的范例：（a）健康肌腱中的慢性机械负荷，以及（b）肌腱病。在前一种负荷范例中，局部肌腱适应性表明某些区域可能“感知到”并因此适应增加的应力水平。在后一种范例中，局部病理特征表明某些肌腱区域可能会“应力屏蔽”并随时间退化。离心运动方案已成功用于肌腱病的治疗，但对其有效性背后的机制了解并不充分。特别是对于附着点性肌腱病，负荷/康复方案的有效性可能取决于运动产生的应力的地形，而不仅仅依赖于所执行的肌肉收缩类型。为了更好地理解肌腱组织的微观力学行为和区域适应性/ malad - 适应性，估计其内部应力应变场很重要。讨论了与肌腱负荷相关的数值技术的近期相关进展。
