Ichinose Hoshizora, Tanaka Fumiko, Yamagishi Takaki, Sado Natsuki, Shiotani Hiroto, Evangelidis Pavlos E, Naito Munekazu, Shibata Shigenobu, Kawakami Yasuo
Graduate School of Sport Sciences, Waseda University, Saitama, Japan.
Human Performance Laboratory, Comprehensive Research Organization of Waseda University, Tokyo, Japan; Faculty of Science and Engineering, Waseda University, Tokyo, Japan.
Exp Gerontol. 2024 Oct 15;196:112574. doi: 10.1016/j.exger.2024.112574. Epub 2024 Sep 6.
Muscle quality is explained by the ratio between muscle size and strength. Conventionally, muscle size is evaluated without considering the composition of contractile and non-contractile tissues in muscle, hence the influence of non-contractile tissues on muscle quality is not fully understood, especially within aging muscle. This study investigated the differences in intramuscular non-contractile tissues between different age and sex groups, and investigated their influence on muscle quality.
Eighty-two older and 64 young females and males participated. Muscle cross-sectional area (quadriceps and hamstrings), separating contractile and non-contractile areas, was calculated from the magnetic resonance image of the right mid-thigh. Maximal voluntary isometric knee extension and flexion torque was measured. Torque/muscle area and torque/contractile area were calculated for each age and sex group.
Non-contractile/muscle area was higher in older than in young individuals in both muscle groups (p < 0.05), and it was greater in the hamstrings than in the quadriceps. For the hamstrings, torque/muscle area was lower in older than in young individuals in both sexes (p < 0.05). However, torque/contractile area did not show the differences between age groups, only between sexes (males>females) (p < 0.05).
The results indicate that 1) the presence of non-contractile tissues varies by age and muscle groups, 2) the extensive presence of non-contractile tissues can contribute to the underestimation of its muscle quality, and 3) the sex differences in muscle quality are influenced by factors other than muscle composition.
肌肉质量由肌肉大小与力量之比来解释。传统上，在评估肌肉大小时未考虑肌肉中收缩性和非收缩性组织的组成，因此非收缩性组织对肌肉质量的影响尚未完全了解，尤其是在衰老肌肉中。本研究调查了不同年龄和性别组肌肉内非收缩性组织的差异，并研究了它们对肌肉质量的影响。
82名老年女性和男性以及64名年轻女性和男性参与了研究。从右大腿中部的磁共振图像计算肌肉横截面积（股四头肌和腘绳肌），并分离出收缩性和非收缩性区域。测量最大自主等长膝关节伸展和屈曲扭矩。计算每个年龄和性别组的扭矩/肌肉面积和扭矩/收缩性面积。
在两个肌肉组中，老年个体的非收缩性/肌肉面积均高于年轻个体（p<0.05），且腘绳肌中的该面积大于股四头肌。对于腘绳肌，老年个体的扭矩/肌肉面积在两性中均低于年轻个体（p<0.05）。然而，扭矩/收缩性面积在年龄组之间未显示出差异，仅在性别之间存在差异（男性>女性）（p<0.05）。
结果表明：1）非收缩性组织的存在因年龄和肌肉组而异；2）非收缩性组织的广泛存在可能导致对其肌肉质量的低估；3）肌肉质量的性别差异受肌肉组成以外的因素影响。
