Kösters A, Wiesinger H P, Bojsen-Møller J, Müller E, Seynnes O R
Department of Sport Science and Kinesiology Salzburg, Austria.
Department of Sport Science and Kinesiology Salzburg, Austria.
Clin Biomech (Bristol). 2014 Mar;29(3):323-9. doi: 10.1016/j.clinbiomech.2013.12.010. Epub 2013 Dec 21.
Rate-dependent properties of tendons have consistently been observed in vitro but in vivo studies comparing the effects of loading duration on this feature remain conflicting. The main purpose of the present study was to evaluate whether tendon loading rate per se would affect in vivo tendon mechanical properties.
Twenty-two physically active male subjects were recruited. Patellar tendon deformation was recorded with ultrasonography under voluntary isometric contractions at rates of 50, 80 and 110Nm/s, controlled via visual feedback.
Subjects were able to accurately generate all three loading rates (Accuracy=2% to 15%), with a greater steadiness at 50 (CV=12.4%) and 110Nm/s (CV=13.1%) than at 80Nm/s (CV=22.9%). Loading rate did not appreciably affect strain or stress. However, stiffness (ɳp(2)=0.555) and Youngs's Modulus (ɳp(2)=0.670) were significantly higher at 80Nm/s (21.4% and 21.6%, respectively) and at 110Nm/s (32.5% and 32.0%, respectively) than at 50Nm/s. Similarly, stiffness and Young's modulus were 9.9% and 8.8% higher, respectively, at 110Nm/s than at 80Nm/s.
These results indicate that in vivo measurements of patellar tendon mechanics are influenced by loading rate. Moreover, they bear important methodological implications for in vivo assessment of mechanical properties of this tendon and possibly other human tendons.
在体外研究中，肌腱的速率依赖性特性一直被观察到，但比较加载持续时间对该特性影响的体内研究结果仍存在矛盾。本研究的主要目的是评估肌腱加载速率本身是否会影响体内肌腱的力学性能。
招募了22名身体活跃的男性受试者。通过视觉反馈控制，在50、80和110 Nm/s的速率下进行自主等长收缩时，用超声记录髌腱变形情况。
受试者能够准确产生所有三种加载速率（准确率=2%至15%），在50 Nm/s（CV=12.4%）和110 Nm/s（CV=13.1%）时比在80 Nm/s（CV=22.9%）时更稳定。加载速率对应变或应力没有明显影响。然而，在80 Nm/s（分别为21.4%和21.6%）和110 Nm/s（分别为32.5%和32.0%）时的刚度（ɳp(2)=0.555）和杨氏模量（ɳp(2)=0.670）显著高于50 Nm/s时。同样，110 Nm/s时的刚度和杨氏模量分别比80 Nm/s时高9.9%和8.8%。
这些结果表明，髌腱力学的体内测量受加载速率影响。此外，它们对该肌腱以及可能其他人体肌腱力学性能的体内评估具有重要的方法学意义。
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