PURPOSE Studies have revealed an age-related decrease in the ability to produce force as well as an increase in the contractile stiffness and passive stress of single muscle fibres. However, further insight into age-related changes to the passive properties of human skeletal muscles is needed. The aim of this study was to characterize single muscle fibre passive properties from young and old males across a physiologic range of sarcomere lengths (SLs). METHODS Ten young ([YM]: mean age: 25.4 years) and ten old ([OM]: mean age: 68.9 years) males participated. Vastus lateralis muscles were biopsied and 182 fibres were tested and analyzed (90 YM and 92 OM) using a cumulative stretch-relaxation protocol. Passive mechanical characteristics of each fibre were obtained by fitting the integral of the logistic function to experimental stress-SL data. RESULTS Muscle fibres from older individuals had significantly greater passive elastic moduli at short SL (1.9-2.65 μm) compared with young (p < 0.05). This resulted in a significantly larger passive stress for SLs between 2.1 μm and 3.55 μm for older individuals when compared with young (p < 0.05). CONCLUSION These results provide novel insight into the length dependency of changes in single muscle fibre passive mechanical properties with age.

中文翻译：

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人类单条肌肉纤维被动弹性特性的年龄相关变化与肌节长度有关。

目的研究已经显示出与年龄相关的力量产生能力的下降，以及单条肌肉纤维的收缩刚度和被动压力的增加。但是，需要进一步了解与年龄相关的人类骨骼肌被动特性的变化。这项研究的目的是在肌节长度（SLs）的生理范围内表征年轻和老年男性的单条肌纤维被动特性。方法十名男性（YM：平均年龄：25.4岁）和十岁（OM）：平均年龄：68.9岁。使用累积的舒张松弛方案对外侧股静脉进行活检，并测试和分析182根纤维（90 YM和92 OM）。通过将逻辑函数的积分拟合到实验应力-SL数据，可以获得每种纤维的被动机械特性。结果与年轻人（p <0.05）相比，来自老年人的肌肉纤维在短SL时（1.9-2.65μm）具有更大的被动弹性模量。与年青人相比，这导致老年人的SL的被动应力明显更大，介于2.1μm和3.55μm之间（p <0.05）。结论这些结果为单肌纤维被动机械性能随年龄变化的长度依赖性提供了新颖的见解。