Sydney Nursing School, The University of Sydney, Sydney, 2050, Australia.
School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, 3086, Australia.
J Muscle Res Cell Motil. 2022 Dec;43(4):173-183. doi: 10.1007/s10974-022-09628-y. Epub 2022 Aug 20.
The single freshly skinned muscle fibre technique was used to investigate Ca- and Sr-activation properties of skeletal muscle fibres from elderly women (66-90 years). Muscle biopsies were obtained from the vastus lateralis muscle. Three populations of muscle fibres were identified according to their specific Sr-activation properties: slow-twitch (type I), fast-twitch (type II) and hybrid (type I/II) fibres. All three fibre types were sampled from the biopsies of 66 to 72 years old women, but the muscle biopsies of women older than 80 years yielded only slow-twitch (type I) fibres. The proportion of hybrid fibres in the vastus lateralis muscle of women of circa 70 years of age (24%) was several-fold greater than in the same muscle of adults (< 10%), suggesting that muscle remodelling occurs around this age. There were no differences between the Ca- and Sr-activation properties of slow-twitch fibres from the two groups of elderly women, but there were differences compared with muscle fibres from young adults with respect to sensitivity to Ca, steepness of the activation curves, and characteristics of the fibre-type dependent phenomenon of spontaneous oscillatory contractions (SPOC) (or force oscillations) occurring at submaximal levels of activation. The maximal Ca activated specific force from all the fibres collected from the seven old women use in the present study was significantly lower by 20% than in the same muscle of adults. Taken together these results show there are qualitative and quantitative changes in the activation properties of the contractile apparatus of muscle fibres from the vastus lateralis muscle of women with advancing age, and that these changes need to be considered when explaining observed changes in women's mobility with aging.
采用新鲜去皮肌纤维技术研究了老年女性（66-90 岁）骨骼肌纤维的钙和锶激活特性。肌肉活检取自股外侧肌。根据其特定的锶激活特性，将三种肌纤维群分为：慢肌（I 型）、快肌（II 型）和混合肌（I/II 型）。所有三种纤维类型都取自 66-72 岁女性的活检样本，但 80 岁以上女性的肌肉活检仅产生慢肌（I 型）纤维。70 岁左右女性股外侧肌中的混合纤维比例（24%）是成年人的数倍（<10%），表明肌肉重塑发生在这个年龄段。两组老年女性的慢肌纤维的钙和锶激活特性没有差异，但与年轻成年人的肌肉纤维相比，钙敏感性、激活曲线的陡度以及自发振荡收缩（SPOC）（或力振荡）纤维类型依赖性现象的特征存在差异，SPOC 发生在低激活水平。在本研究中，从 7 位老年女性收集的所有纤维的最大钙激活比肌力均显著降低 20%，低于成年人的同一肌肉。综上所述，这些结果表明，随着年龄的增长，女性股外侧肌纤维收缩装置的激活特性发生了定性和定量的变化，在解释女性随年龄增长的活动能力变化时需要考虑这些变化。
