Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
Ann Biomed Eng. 2013 Jun;41(6):1120-8. doi: 10.1007/s10439-013-0796-4. Epub 2013 Apr 3.
Tendon mechanical properties are thought to degrade during aging but improve with exercise. A remaining question is whether exercise in aged animals provides sufficient regenerative, systemic stimulus to restore younger mechanical behaviors. Herein we address that question with tail tendons from aged and exercised rats, which would be subject to systemic effects but not direct loading from the exercise regimen. Twenty-four month old rats underwent one of three treadmill exercise training protocols for 12 months: sedentary (walking at 0° incline for 5 min/day), moderate (running at 0° incline for 30 min/day), or high (running at 4° incline for 30 min/day). A group of 9 month old rats were used to provide an adult control, while a group of 3 month old rats provided a young control. Tendons were harvested at sacrifice and mechanically tested. Results show significant age-dependent differences in modulus, ultimate stress, relaxation rate, and percent relaxation. Relaxation rate was strain-dependent, consistent with nonlinear superposition or Schapery models but not with quasilinear viscoelasticity (QLV). Trends in exercise data suggest that with exercise, tendons assume the elastic character of younger rats (lower elastic modulus and ultimate stress).
肌腱的力学性能被认为随着年龄的增长而降低，但通过锻炼可以得到改善。一个悬而未决的问题是，老年动物的锻炼是否能提供足够的再生、系统性刺激，以恢复更年轻的力学行为。在这里，我们用老年和锻炼后的大鼠的尾巴肌腱来回答这个问题，这些肌腱会受到系统性的影响，但不会受到锻炼方案的直接影响。24 个月大的大鼠接受了三种跑步机运动训练方案中的一种，持续 12 个月：久坐（每天以 0°的坡度行走 5 分钟）、适度（每天以 0°的坡度跑步 30 分钟）或高强度（每天以 4°的坡度跑步 30 分钟）。一组 9 个月大的大鼠被用来作为成年对照组，而一组 3 个月大的大鼠则作为年轻对照组。在处死时采集肌腱并进行力学测试。结果表明，肌腱的模量、极限应力、松弛率和松弛百分比存在显著的年龄依赖性差异。松弛率与应变有关，与非线性超叠加或 Schapery 模型一致，但与准线性粘弹性（QLV）不一致。锻炼数据的趋势表明，随着锻炼，肌腱呈现出年轻大鼠的弹性特征（较低的弹性模量和极限应力）。
