Pennington Biomedical Research Center, LSU System, Baton Rouge, LA, USA.
Department of Mathematical Sciences, United States Military Academy West Point, West Point, NY, USA.
J Cachexia Sarcopenia Muscle. 2022 Apr;13(2):1100-1112. doi: 10.1002/jcsm.12959. Epub 2022 Feb 15.
Body mass is the primary metabolic compartment related to a vast number of clinical indices and predictions. The extent to which skeletal muscle (SM), a major body mass component, varies between people of the same sex, weight, height, and age is largely unknown. The current study aimed to explore the magnitude of muscularity variation present in adults and to examine if variation in muscularity associates with other body composition and metabolic measures.
Muscularity was defined as the difference (residual) between a person's actual and model-predicted SM mass after controlling for their weight, height, and age. SM prediction models were developed using data from a convenience sample of 492 healthy non-Hispanic (NH) White adults (ages 18-80 years) who had total body SM and SM surrogate, appendicular lean soft tissue (ALST), measured with magnetic resonance imaging and dual-energy X-ray absorptiometry, respectively; residual SM (SM ) and ALST were expressed in kilograms and kilograms per square meter. ALST mass was also evaluated in a population sample of 8623 NH-White adults in the 1999-2006 National Health and Nutrition Examination Survey. Associations between muscularity and variation in the residual mass of other major organs and tissues and resting energy expenditure were evaluated in the convenience sample.
The SM, on average, constituted the largest fraction of body weight in men and women up to respective BMIs of 35 and 25 kg/m . SM in the convenience sample varied widely with a median of 31.2 kg and an SM inter-quartile range/min/max of 3.35 kg/-10.1 kg/9.0 kg in men and 21.1 kg and 2.59 kg/-7.2 kg/7.5 kg in women; per cent of body weight as SM at 25th and 75th percentiles for men were 33.1% and 39.6%; corresponding values in women were 24.2% and 30.8%; results were similar for SM indices and for ALST measures in the convenience and population samples. Greater muscularity in the convenience sample was accompanied by a smaller waist circumference (men/women: P < 0.001/=0.085) and visceral adipose tissue (P = 0.014/0.599), larger liver (P = 0.065/<0.001), kidneys (P = 0.051/<0.009), and bone mineral (P < 0.001/<0.001), and larger magnitude resting energy expenditure (P < 0.001/<0.001) than predicted for the same sex, age, weight, and height.
Muscle mass is the largest body compartment in most adults without obesity and is widely variable in mass across people of similar body size and age; and high muscularity is accompanied by distinct body composition and metabolic characteristics. This previously unrecognized heterogeneity in muscularity in the general population has important clinical and research implications.
体重是与大量临床指标和预测相关的主要代谢成分。在相同性别、体重、身高和年龄的人群中，骨骼肌（SM）这一体重主要成分的变化程度在很大程度上尚不清楚。本研究旨在探讨成年人肌肉变化的幅度，并研究肌肉变化与其他身体成分和代谢指标的关系。
肌肉量定义为在控制体重、身高和年龄后，个体实际肌肉量与模型预测肌肉量之间的差异（残差）。SM 预测模型是使用方便样本中的 492 名健康非西班牙裔（NH）白种成年人（年龄 18-80 岁）的数据开发的，这些成年人的全身 SM 和 SM 替代物，四肢瘦软组织（ALST）分别通过磁共振成像和双能 X 射线吸收法测量；SM 的残差（SM）和 ALST 以千克和千克/平方米表示。在 NH-White 成年人的 1999-2006 年全国健康和营养检查调查的人群样本中也评估了 ALST 质量。在方便样本中评估了肌肉量与其他主要器官和组织的残差质量和静息能量消耗之间的关系。
在 BMI 分别为 35 和 25kg/m 的范围内，SM 平均占男性和女性体重的最大比例。方便样本中的 SM 变化范围很大，中位数为 31.2kg，SM 四分位距/最小值/最大值为男性 3.35kg/-10.1kg/9.0kg，女性 2.59kg/-7.2kg/7.5kg；第 25 和 75 百分位数时，男性的体脂百分比为 33.1%和 39.6%，女性相应值为 24.2%和 30.8%；在方便样本和人群样本中，SM 指数和 ALST 测量结果相似。方便样本中肌肉量较大的人腰围较小（男性/女性：P<0.001/=0.085），内脏脂肪组织（P=0.014/0.599）、肝脏（P=0.065/＜0.001）、肾脏（P=0.051/＜0.009）和骨矿物质（P＜0.001/＜0.001）也较大，静息能量消耗（P＜0.001/＜0.001）也较大，与相同性别、年龄、体重和身高预测的水平不同。
肌肉质量是大多数成年人中最大的身体成分，在相似体型和年龄的人群中，肌肉质量变化很大；肌肉质量高与明显的身体成分和代谢特征有关。在普通人群中，肌肉质量的这种以前未被认识到的异质性具有重要的临床和研究意义。
