Franz Jason R, Thelen Darryl G
Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, USA.
Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
J Biomech. 2016 Jun 14;49(9):1403-1410. doi: 10.1016/j.jbiomech.2016.04.032. Epub 2016 May 3.
The Achilles tendon (AT) is a complex structure, consisting of distinct fascicle bundles arising from each triceps surae muscle that may act as mechanically independent structures. Advances in tissue imaging are rapidly accelerating our understanding of the complexities of functional Achilles tendon behavior, with potentially important implications for musculoskeletal injury and performance. In this overview of our recent contributions to these efforts, we present the results of complementary experimental and computational approaches to investigate AT behavior during walking and its potential relevance to reduced triceps surae mechanical performance due to aging. Our experimental evidence reveals that older tendons exhibit smaller differences in tissue deformations than young adults between regions of the AT presumed to arise from the gastrocnemius and soleus muscles. These observations are consistent with a reduced capacity for inter-fascicle sliding within the AT, which could have implications for the mechanical independence of the triceps surae muscles. More uniform AT deformations are also correlated with hallmark biomechanical features of elderly gait - namely, a loss of net ankle moment, power, and positive work during push-off. Simulating age-related reductions in the capacity for inter-fascicle sliding in the AT during walking predicts detriments in gastrocnemius muscle-tendon mechanical performance coupled with underlying shifts in fascicle kinematics during push-off. AT compliance, also suspected to vary due to age, systematically modulates those effects. By integrating in vivo imaging with computational modeling, we have gained theoretical insight into multi-scale biomechanical changes due to aging, hypotheses regarding their functional effects, and opportunities for experiments that validate or invalidate these assertions.
跟腱（AT）是一个复杂的结构，由来自每块小腿三头肌的不同肌束组成，这些肌束可能作为机械上独立的结构发挥作用。组织成像技术的进步正在迅速加速我们对功能性跟腱行为复杂性的理解，这对肌肉骨骼损伤和运动表现可能具有重要意义。在本综述中，我们介绍了我们近期在这些研究方面的成果，展示了互补的实验和计算方法的结果，以研究步行过程中的跟腱行为及其与因衰老导致的小腿三头肌机械性能下降的潜在关联。我们的实验证据表明，与年轻人相比，老年跟腱在假定来自腓肠肌和比目鱼肌的区域之间，组织变形的差异更小。这些观察结果与跟腱内肌束间滑动能力下降一致，这可能对小腿三头肌的机械独立性产生影响。更均匀的跟腱变形也与老年人步态的标志性生物力学特征相关——即蹬离期净踝关节力矩、功率和正功的丧失。模拟步行过程中与年龄相关的跟腱内肌束间滑动能力下降，预测了腓肠肌肌腱机械性能的损害以及蹬离期肌束运动学的潜在变化。跟腱顺应性也被怀疑会因年龄而变化，它会系统地调节这些影响。通过将体内成像与计算建模相结合，我们在理论上深入了解了衰老引起的多尺度生物力学变化、关于其功能影响的假设以及验证或推翻这些论断的实验机会。
