Tomlinson D J, Erskine R M, Winwood K, Morse C I, Onambélé G L
Department of Exercise and Sport Science, Institute for Performance Research, Manchester Metropolitan University, Crewe, UK.
J Anat. 2014 Dec;225(6):675-84. doi: 10.1111/joa.12248. Epub 2014 Oct 14.
It is unknown whether loading of the lower limbs through additional storage of fat mass as evident in obesity would promote muscular adaptations similar to those seen with resistance exercise. It is also unclear whether ageing modulates any such adjustments. This study aimed to examine the relationships between adiposity, ageing and skeletal muscle size and architecture. A total of 100 untrained healthy women were categorised by age into young (Y) (mean ± SD: 26.7 ± 9.4 years) vs. old (O) (65.1 ± 7.2 years) and body mass index (BMI) classification (underweight, normal weight, overweight and obese). Participants were assessed for body fat using dual energy x-ray absorptiometry, and for gastrocnemius medialis (GM) muscle architecture (skeletal muscle fascicle pennation angle and length) and size [GM muscle volume and physiological cross-sectional area (PCSA)] using B-mode ultrasonography. GM fascicle pennation angle (FPA) in the obese Y females was 25% greater than underweight (P = 0.001) and 25% greater than normal weight (P = 0.001) individuals, while O females had 32 and 22% greater FPA than their underweight (P = 0.008) and normal weight (P = 0.003) counterparts. Furthermore, FPA correlated with body mass in both Y and O females (Y r = 0.303; P < 0.001; O r = 0.223; P = 0.001), yet no age-related differences in the slope or r-values were observed (P > 0.05). Both GM muscle volume (P = 0.003) and PCSA (P = 0.004) exhibited significant age × BMI interactions. In addition, muscle volume and PCSA correlated with BMI, body mass and fat mass. Interestingly, ageing reduced both the degree of association in these correlations (P < 0.05) and the slope of the regressions (P < 0.05). Our findings partly support our hypotheses in that obesity-associated changes in GM PCSA and volume differed between the young and old. The younger GM muscle adapted to the loading induced by high levels of body mass, adiposity and BMI by increasing its volume and increasing its pennation angle, ultimately enabling it to produce higher maximum torque. Such an adaptation to increased loading did not occur in the older GM muscle. Nonetheless, the older GM muscle FPA increased to a similar extent to that seen in young GM muscle, an effect which partly explains the relatively enhanced absolute maximum torque observed in obese older females.
肥胖时下肢因脂肪量额外储存而增加的负荷，是否会促进类似于抗阻运动所产生的肌肉适应性变化，目前尚不清楚。同样不清楚的是，衰老是否会调节这种适应性变化。本研究旨在探讨肥胖、衰老与骨骼肌大小和结构之间的关系。总共100名未经训练的健康女性，按年龄分为年轻组（Y）（平均±标准差：26.7±9.4岁）和老年组（O）（65.1±7.2岁），并根据体重指数（BMI）分类（体重过轻、正常体重、超重和肥胖）。使用双能X线吸收法评估参与者的体脂，使用B型超声评估腓肠肌内侧头（GM）的肌肉结构（骨骼肌束状羽状角和长度）和大小[GM肌肉体积和生理横截面积（PCSA）]。肥胖的年轻女性GM束状羽状角（FPA）比体重过轻的女性大25%（P = 0.001），比正常体重的女性大25%（P = 0.001），而老年女性的FPA比体重过轻（P = 0.008）和正常体重（P = 0.003）的同龄人分别大32%和22%。此外，年轻和老年女性的FPA均与体重相关（年轻组r = 0.303；P < 0.001；老年组r = 0.223；P = 0.001），但在斜率或r值上未观察到与年龄相关的差异（P > 0.05）。GM肌肉体积（P = 0.003）和PCSA（P = 0.004）均表现出显著的年龄×BMI交互作用。此外，肌肉体积和PCSA与BMI、体重和脂肪量相关。有趣的是，衰老降低了这些相关性的关联程度（P < 0.05）和回归斜率（P < 0.05）。我们的研究结果部分支持了我们的假设，即肥胖相关的GM PCSA和体积变化在年轻人和老年人中有所不同。年轻的GM肌肉通过增加其体积和羽状角来适应高水平体重、肥胖和BMI所带来的负荷，最终使其能够产生更高的最大扭矩。而老年GM肌肉并未发生这种对增加负荷的适应性变化。尽管如此，老年GM肌肉的FPA增加幅度与年轻GM肌肉相似，这一效应部分解释了在肥胖老年女性中观察到的相对增强的绝对最大扭矩。
