Ageing is associated with alterations in the structure and function of the contractile and elastic tissues that enable movement, posture, and balance. Alterations in structure and mechanical properties of the ankle plantarflexors and Achilles tendon are of particular interest due to their important ‘catapult-like’ function during efficient and healthy human locomotion. In this study, we examined age-related differences in the in vivo mechanical properties of both muscle and tendon in the human ankle plantarflexors in healthy younger (21 ± 3.25 years) and older (69 ± 2.86 years) adults. All participants were physically active, to represent healthy ageing. B-mode ultrasound coupled with force measurements was used to determine in vivo Achilles tendon stiffness and shear-wave elastography was used to measure shear modulus, an index of muscle stiffness, in the medial and lateral gastrocnemii. We found that older adults displayed 43% lower (p = 0.004) Achilles tendon stiffness, 59% lower (p < 0.001) Achilles tendon Young’s modulus, and 34% greater (p = 0.002) Achilles tendon cross-sectional area compared to younger participants. We found no difference in the shear modulus of the medial or lateral gastrocnemii between the younger and older individuals. The reduction in Achilles tendon stiffness coupled with similar gastrocnemii muscle shear modulus likely influences the integrated neuromechanical function of the ankle plantarflexor muscle–tendon units during locomotor tasks. Further investigations into the relationship between altered mechanical properties and in vivo muscle–tendon dynamics will provide greater insights into the age-related declines in mobility and locomotor function.

衰老与使运动，姿势和平衡得以实现的收缩和弹性组织的结构和功能的改变有关。由于脚踝flex屈肌和跟腱的结构和机械性能发生了变化，这是因为它们在有效而健康的人体运动过程中起着重要的“类似催化作用”的作用。在这项研究中，我们检查了健康的年轻人（21±3.25岁）和老年人（69±2.86岁）的人脚踝屈肌的肌肉和肌腱的体内力学性能的年龄相关差异。所有参与者都身体活跃，代表着健康的老龄化。B型超声结合力测量用于确定体内跟腱僵硬和剪切波弹性成像用于测量内侧腓肠肌和外侧腓肠肌的剪切模量，这是肌肉僵硬的指标。我们发现，与年轻的参与者相比，老年人的跟腱僵硬度降低了43％（p = 0.004），跟腱刚度降低了59％（p <0.001），跟腱横截面积增大了34％（p = 0.002）。 。我们发现年轻和老年人之间内侧或外侧腓肠肌的剪切模量没有差异。跟腱肌腱僵硬度的降低以及类似的腓肠肌肌肉剪切模量可能会影响运动任务期间踝plant屈肌腱单元的综合神经力学功能。进一步研究改变的机械性能与体内肌肉-肌腱动力学将提供与年龄相关的运动能力和运动功能下降的更多见解。