Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK; Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Leahurst Campus, Neston CH64 7TE, UK.
School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
Acta Biomater. 2014 Jul;10(7):3217-24. doi: 10.1016/j.actbio.2014.04.008. Epub 2014 Apr 18.
Tendons can broadly be categorized according to their function: those that act purely to position the limb and those that have an additional function as energy stores. Energy-storing tendons undergo many cycles of large deformations during locomotion, and so must be able to extend and recoil efficiently, rapidly and repeatedly. Our previous work has shown rotation in response to applied strain in fascicles from energy-storing tendons, indicating the presence of helical substructures which may provide greater elasticity and recovery. In the current study, we assessed how preconditioning and fatigue loading affect the ability of fascicles from the energy-storing equine superficial digital flexor tendon to extend and recoil. We hypothesized that preconditioned samples would exhibit changes in microstructural strain response, but would retain their ability to recover. We further hypothesized that fatigue loading would result in sample damage, causing further alterations in extension mechanisms and a significant reduction in sample recovery. The results broadly support these hypotheses: preconditioned samples showed some alterations in microstructural strain response, but were able to recover following the removal of load. However, fatigue loaded samples showed visual evidence of damage and exhibited further alterations in extension mechanisms, characterized by decreased rotation in response to applied strain. This was accompanied by increased hysteresis and decreased recovery. These results suggest that fatigue loading results in a compromised helix substructure, reducing the ability of energy-storing tendons to recoil. A decreased ability to recoil may lead to an impaired response to further loading, potentially increasing the likelihood of injury.
一类是纯粹用于定位肢体的肌腱，另一类是具有储能功能的肌腱。在运动过程中，储能肌腱会经历许多次大变形循环，因此必须能够有效地、快速地、反复地伸展和回弹。我们之前的工作表明，在储能肌腱的束中，纤维对施加的应变会产生旋转，这表明存在螺旋亚结构，这可能提供更大的弹性和恢复能力。在当前的研究中，我们评估了预条件和疲劳加载对储能马浅表背侧屈肌腱束伸展和回弹能力的影响。我们假设预条件的样本会表现出微观结构应变响应的变化，但仍能保持其恢复能力。我们进一步假设，疲劳加载会导致样本损伤，进一步改变伸展机制，并显著降低样本的恢复能力。结果大致支持这些假设：预条件的样本显示出微观结构应变响应的一些变化，但在负载移除后能够恢复。然而，疲劳加载的样本显示出损伤的明显迹象，并表现出进一步改变的伸展机制，其特征是对施加应变的旋转减少。这伴随着滞后增加和恢复减少。这些结果表明，疲劳加载会导致螺旋亚结构受损，从而降低储能肌腱的回弹能力。回弹能力的降低可能导致对进一步加载的反应受损，从而增加受伤的可能性。
