肌腱的運動訓練及其適應

Tendon sport training and adaptation

肌腱接受長期運動的力學負重（mechanical loading）的訓練，會改變其力學性質，造成組織膠原的更迭（collagen turnover），提升肌腱的勁度（stiffness）、楊氏模量（Young's modulus）及橫斷面面積（cross section area, CSA），使其增加承受負重的能力。反之，久坐生活型態，缺乏運動或力學刺激時，顯著導致膠原及肌腱更迭（tendon turnover）的下降。肌腱強化除了可以提高運動表現，亦為預防運動傷害的重要手段。肌腱訓練的變數為應變幅度（strain magnitude）與應變率（strain rate），其相對應的訓練方法為阻力訓練（resistance training）與增強式動作（plyometric exercises）的爆發力訓練，訓練強度愈高，對於結締組織的刺激愈大，強化效果愈佳，然而，仍宜以負荷漸進的方式進行之。另一個訓練變數為應變分佈（strain distribution），其強化肌腱部位是局部的，為了避免造成肌腱不均勻的應變分佈，宜注意從各個角度與方向強化肌腱，以各關節的三軸不同動作方向，全面均勻的強化肌腱，不宜只強化特定局部肌腱，使得沒有強化的部位，成為肌腱的弱點，進而引起運動傷害。對於人體，肌腱產生適應的時間久於神經及肌肉，甚至可達3~4倍之久，因此，造成適應上的失衡（imbalanced adaptation），訓練肌腱時，需要更多的耐心，方能產生有效適應，以維持肌肉與肌腱力量之間的平衡，使肌腱產生最佳化發展，以奠定最大肌力暨爆發力表現的基礎及減少運動傷害的機會。青少年的肌腱適應原則上與成人類似，但其適應反應（adaptive response）似乎更敏銳。如果要更有效率的訓練肌腱，宜趁著青少年階段，當肌腱處於適應較為敏銳的階段，否則成熟之後，肌腱接受刺激的反應就會較為遲鈍，訓練的效果較不顯著。

Engaging in long-term mechanical load training will alter the mechanical properties of tissues, resulting in tendon collagen turnover. This change increases tendon stiffness, Young’s modulus, and cross-sectional areas, thereby enhancing the load-bearing capacity of tendons. Conversely, a sedentary lifestyle, characterized by a lack of physical activities or mechanical stimuli, leads to considerable decreases in collagen and tendon turnover. Strengthening tendons not only improves athletic performance but also plays a crucial role in preventing sports injuries. The variables in tendon training include strain magnitude and strain rate, which correspond to training methods such as resistance training and explosive plyometric exercises. The higher the intensity of the training, the greater the stimulus on the connective tissues and the better the strengthening effect. However, one is advised to increase the load gradually. Another training variable, strain distribution, focuses on strengthening local tendons. To avoid uneven tendon strength distribution, one should strengthen tendons from various angles and directions. Tendons should be comprehensively and evenly strengthened in all three axes of motion for each joint. This approach prevents overemphasis on specific local tendons, which could leave untrained areas as weak points and lead to sports injuries. In humans, compared with nerves and muscles, tendons take substantially longer to adapt－up to three to four times longer. This results in imbalanced adaptation, requiring more patience during tendon training to effectively foster adaptation and maintain a balance between muscle and tendon strength. Optimal tendon development lays the foundation for athletic performance and reduces the risk of sports injuries. In principle, tendon adaptation in youths is similar to that in adults, but the adaptive response in youths appears to be more subtle. Thus, for more efficient tendon training, training during youths when tendons are more responsive to adaptation is optimal. Once matured, tendons become less responsive to stimuli, making the training effects less pronounced.