Abe T, Kearns C F, Fukunaga T
Tokyo Metropolitan University, Tokyo, Japan.
Br J Sports Med. 2003;37(5):436-40. doi: 10.1136/bjsm.37.5.436.
To determine sex differences in the distribution of regional and total skeletal muscle (SM) using contiguous whole body magnetic resonance imaging (MRI) data, and to examine the relations between fat free mass (FFM) and total and regional SM masses.
A total of 20 Japanese college students (10 women and 10 men) volunteered for the study. FFM was measured by two compartment densitometry. Whole body MRI images were prepared using a 1.5 T scanner. Contiguous transverse images with 1.0 cm slice thickness were obtained from the first cervical vertebra to the ankle joints. All MRI scans were segmented into four components (SM, subcutaneous adipose tissue, bone, and residual tissues). In each slice, the SM tissue cross sectional areas (CSAs) were digitised, and the muscle tissue volume per slice was calculated by multiplying muscle CSA by slice thickness. SM volume units (litres) were converted into mass units (kg) by multiplying the volumes by the assumed constant density (1.041 mg/ml) for SM.
The SM distribution pattern (shape of curve) from the contiguous whole body slices was essentially similar for the two sexes, with two large peaks and three smaller peaks (arms excluded). However, the largest peak was observed at the upper portion of the thigh for women and at the level of the shoulder for men. Men had larger (p<0.01) total and regional SM mass than women. All regional SM masses correlated highly (r=0.90-0.99, p<0.01) with total SM mass. A strong positive correlation was observed between FFM and total and regional SM masses in both sexes (women, r=0.95; men, r=0.90; all p<0.01). As FFM increased, there was a corresponding increase in SM/FFM ratio for all subjects (r=0.86, p<0.01).
Sex differences in total SM/FFM ratio and regional SM distributions are associated with the degree of absolute FFM accumulation in men and women.
利用连续的全身磁共振成像（MRI）数据确定区域和全身骨骼肌（SM）分布的性别差异，并研究去脂体重（FFM）与全身及区域SM质量之间的关系。
共有20名日本大学生（10名女性和10名男性）自愿参与本研究。通过两室密度测定法测量FFM。使用1.5T扫描仪制备全身MRI图像。从第一颈椎至踝关节获取层厚为1.0cm的连续横断图像。所有MRI扫描均被分割为四个部分（SM、皮下脂肪组织、骨骼和残余组织）。在每一层中，将SM组织的横截面积（CSA）数字化，并通过将肌肉CSA乘以层厚来计算每层的肌肉组织体积。通过将体积乘以假定的SM恒定密度（1.041mg/ml），将SM体积单位（升）转换为质量单位（千克）。
两性连续全身切片的SM分布模式（曲线形状）基本相似，有两个大峰和三个小峰（不包括手臂）。然而，女性最大的峰出现在大腿上部，男性则出现在肩部水平。男性的全身和区域SM质量均大于女性（p<0.01）。所有区域SM质量与全身SM质量高度相关（r=0.90-0.99，p<0.01）。在两性中，FFM与全身及区域SM质量之间均观察到强正相关（女性，r=0.95；男性，r=0.90；均p<0.01）。随着FFM增加，所有受试者的SM/FFM比值相应增加（r=0.86，p<0.01）。
全身SM/FFM比值和区域SM分布的性别差异与男性和女性FFM的绝对积累程度有关。
