Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada; School of Kinesiology, Faculty of Education, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada.
Exp Gerontol. 2021 Jul 15;150:111348. doi: 10.1016/j.exger.2021.111348. Epub 2021 Apr 14.
Natural adult aging is associated with declines in skeletal muscle performance, including impaired Ca sensitivity and a slowing of rapid force production (rate of force redevelopment; k). The purpose of this study was to investigate the relationship between impaired Ca sensitivity and k of single muscle fibres from young and older adults. Participants included 8 young (22-35 yrs) and 8 older (60-81 yrs) males who were living independently. A percutaneous muscle biopsy of the vastus lateralis of each participant was performed. Single muscle fibre mechanical tests included maximal Ca-activated force (P), force-pCa curves, and k. We showed a decrease in pCa in old type II fibres compared to young, indicating impaired Ca sensitivity in older adults. The k behaved in a Ca-dependent manner such that with increasing [Ca], k increases, to a plateau. Interestingly, k was not different between young and old muscle fibres. Furthermore, we found strong associations between pCa and k in both old type I and type II fibres, such that those fibres with lower Ca sensitivity had a slowed k. This Ca association, combined with impaired Ca handling in older adults suggests a potential Ca-dependent mechanism affecting the transition from weakly- to strongly-bound cross-bridge states, leading to a decline in skeletal muscle performance. Future research is needed to explore the role alterations to Ca sensitivity/handling could be playing in age-related whole muscle performance declines.
自然衰老与骨骼肌功能下降有关，包括钙敏感性降低和快速力量产生（力再发展速率；k）减慢。本研究旨在探讨年轻和老年个体的单个肌纤维钙敏感性和 k 之间的关系。参与者包括 8 名年轻（22-35 岁）和 8 名老年（60-81 岁）男性，他们均独立生活。对每位参与者的股外侧肌进行经皮肌肉活检。单个肌纤维力学测试包括最大 Ca 激活力（P）、力-pCa 曲线和 k。与年轻个体相比，老年 II 型纤维的 pCa 降低，表明老年个体钙敏感性降低。k 以 Ca 依赖性方式表现，即随着[Ca]的增加，k 增加，达到平台。有趣的是，年轻和老年肌纤维之间的 k 没有差异。此外，我们在年轻和老年 I 型和 II 型纤维中均发现 pCa 和 k 之间存在强烈关联，即那些钙敏感性较低的纤维 k 较慢。这种 Ca 相关性，加上老年人 Ca 处理能力受损，表明潜在的 Ca 依赖性机制可能影响从弱结合到强结合横桥状态的转变，导致骨骼肌功能下降。需要进一步的研究来探讨 Ca 敏感性/处理的改变在与年龄相关的整个肌肉性能下降中可能发挥的作用。
