School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia.
School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia; School of Science, Technology, and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland, Australia.
J Biomech. 2021 Dec 2;129:110823. doi: 10.1016/j.jbiomech.2021.110823. Epub 2021 Oct 22.
When muscles contract and change length, they also bulge in thickness and/or width. These shape changes extend the functional range of skeletal muscle by allowing individual muscle fibres to shorten at different velocities than the whole muscle. Age-related differences in muscle architecture and tissue properties influence how older muscles change shape and architecture during contractions, yet this remains unexplored in active older adults. The aim of this study was to quantify and compare in vivo muscle architecture and shape changes in the medial (MG) and lateral (LG) gastrocnemii of active younger and older adults during isometric plantarflexion contractions. Fifteen younger (21 ± 2y) and 15 older (70 ± 3y) participants performed contractions at 20%, 40%, 60%, 80%, and 100% of maximum voluntary contraction (MVC). B-mode ultrasound was used to measure fascicle length, pennation angle and muscle thickness in MG and LG. We found no influence of age on changes in normalized fascicle length and thickness, or absolute change in pennation angle during contractions. With increasing contraction level, MG and LG fascicle shortening (P < 0.001) and rotation (P < 0.001) increased. However, the change in muscle thickness increased at higher contraction levels in LG, and not MG. Similarly, increased changes in pennation angle were associated with increased muscle thickness in LG, but not MG at 80% and 100% MVC. These results suggest that (1) gastrocnemii shape changes are similar in active older and younger adults at matched levels of effort, and (2) the relationship between pennation angle and muscle thickness can differ between synergistics (LG and MG) and across contraction levels.
当肌肉收缩并改变长度时，它们的厚度和/或宽度也会向外突出。这些形状变化通过允许单个肌纤维以比整块肌肉不同的速度缩短，从而扩展了骨骼肌的功能范围。肌肉结构和组织特性的年龄相关差异会影响老年人肌肉在收缩过程中如何改变形状和结构，但这在活跃的老年人中尚未得到探索。本研究的目的是在等长跖屈收缩过程中，定量和比较活跃的年轻和老年成年人内侧（MG）和外侧（LG）比目鱼肌的肌肉结构和形状变化。15 名年轻（21 ± 2 岁）和 15 名老年（70 ± 3 岁）参与者以 20%、40%、60%、80%和 100%最大自主收缩（MVC）的水平进行收缩。B 型超声用于测量 MG 和 LG 中的肌束长度、肌束羽状角和肌肉厚度。我们发现年龄对收缩过程中肌束长度和厚度的归一化变化或羽状角的绝对变化没有影响。随着收缩水平的增加，MG 和 LG 肌束缩短（P < 0.001）和旋转（P < 0.001）增加。然而，在 LG 中，随着收缩水平的增加，肌肉厚度的变化增加，但在 MG 中则不然。同样，羽状角的变化增加与 LG 中肌肉厚度的增加相关，但在 80%和 100%MVC 时与 MG 无关。这些结果表明：（1）在匹配的努力水平下，活跃的老年和年轻成年人的比目鱼肌形状变化相似；（2）羽状角和肌肉厚度之间的关系可能在协同肌（LG 和 MG）之间和收缩水平之间有所不同。
