Carroll C C, Dickinson J M, Haus J M, Lee G A, Hollon C J, Aagaard P, Magnusson S P, Trappe T A
Human Performance Laboratory, Ball State Univ., Muncie, IN 47306, USA.
J Appl Physiol (1985). 2008 Dec;105(6):1907-15. doi: 10.1152/japplphysiol.00059.2008. Epub 2008 Oct 16.
Tendons are important for optimal muscle force transfer to bone and play a key role in functional ability. Changes in tendon properties with aging could contribute to declines in physical function commonly associated with aging. We investigated the in vivo mechanical properties of the patellar tendon in 37 men and women [11 young (27 +/- 1 yr) and 26 old (65 +/- 1 yr)] using ultrasonography and magnetic resonance imaging (MRI). Patella displacement relative to the tibia was monitored with ultrasonography during ramped isometric contractions of the knee extensors, and MRI was used to determine tendon cross-sectional area (CSA) and signal intensity. At peak force, patellar tendon deformation, stress, and strain were 13 (P = 0.05), 19, and 12% less in old compared with young (P < 0.05). Additionally, deformation, stiffness, stress, CSA, and length were 18, 35, 41, 28, and 11% greater (P < 0.05), respectively, in men compared with women. After normalization of mechanical properties to a common force, no age differences were apparent; however, stress and strain were 26 and 22% higher, respectively, in women compared with men (P < 0.05). CSA and signal intensity decreased 12 and 24%, respectively, with aging (P < 0.05) in the midregion of the tendon. These data suggest that differences in patellar tendon in vivo mechanical properties with aging are more related to force output rather than an age effect. In contrast, the decrease in signal intensity indirectly suggests that the internal milieu of the tendon is altered with aging; however, the physiological and functional consequence of this finding requires further study.
肌腱对于肌肉力量向骨骼的最佳传递非常重要，并且在功能能力方面发挥关键作用。随着年龄增长，肌腱特性的变化可能导致与衰老相关的身体功能下降。我们使用超声和磁共振成像（MRI）研究了37名男性和女性[11名年轻人（27±1岁）和26名老年人（65±1岁）]髌腱的体内力学特性。在膝关节伸肌等长收缩过程中，通过超声监测髌骨相对于胫骨的位移，并使用MRI确定肌腱横截面积（CSA）和信号强度。在峰值力时，与年轻人相比，老年人的髌腱变形、应力和应变分别减少了13%（P = 0.05）、19%和12%（P < 0.05）。此外，与女性相比，男性的变形、刚度、应力、CSA和长度分别增加了18%、35%、41%、28%和11%（P < 0.05）。在将力学特性归一化为共同力后，未发现年龄差异；然而，与男性相比，女性的应力和应变分别高出26%和22%（P < 0.05）。随着年龄增长，肌腱中部的CSA和信号强度分别下降了12%和24%（P < 0.05）。这些数据表明，髌腱体内力学特性随年龄的差异更多地与力输出有关，而非年龄效应。相比之下，信号强度的降低间接表明肌腱的内部环境随年龄而改变；然而，这一发现的生理和功能后果需要进一步研究。
