Skeletal muscle and abdominal circumference explain intramuscular fat, independent of exercise frequency, in middle-aged Japanese men

• Published in: PloS one 2022-05, Vol.17 (5), p.e0267557-e0267557
• Main Authors: Akima, Hiroshi, Maeda, Hisashi, Suwa, Masataka, Imoto, Takayuki, Tanaka, Noriko
• Format: Article
• Language: English
• Subjects: Abdomen; Adipose tissue; Age; Alcohol; Analysis; Biology and Life Sciences; Blood pressure; Body composition; Body fat; Body mass; Body mass index; Body size; Computed tomography; Dependent variables; Exercise; Habits; Image acquisition; Image processing; Independent variables; Medicine and Health Sciences; Metabolism; Middle age; Multiple regression analysis; Muscles; Musculoskeletal system; Physical characteristics; Physical fitness; Physical properties; Questionnaires; Regression analysis; Skeletal muscle; Smoking; Strength training; Trunk muscles; Umbilicus; Variables; Variance analysis
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0267557

The purpose of this study was to examine how intramuscular adipose tissue (IntraMAT) can be characterized using physical and functional characteristics, muscle size, and/or adipose tissue in four different exercise frequency groups of middle-aged Japanese men. One thousand twenty-eight middle-aged men (age, 47.5 ± 8.1 years; height, 170.5 ± 5.8 cm; body mass, 67.0 ± 9.3 kg; body mass index, 21.9 ± 5.3 kg/m2) were allocated to four groups on the basis of their weekly exercise frequency: Group 1, no exercise, n = 334; Group 2, once a week, n = 271; Group 3, a few days a week, n = 269; and Group 4, every day, n = 154. Their body composition, blood pressure, and handgrip strength were assessed. A single-slice computerized tomography image at the level of the umbilicus was acquired and the CSAs of IntraMAT, muscle tissue, and subcutaneous and visceral adipose tissues (SCAT and VAT) were calculated. The %IntraMAT significantly correlated with physical characteristics, such as age, BMI, abdominal circumference, and muscle tissue CSA. Stepwise multiple regression analysis was performed, with the %IntraMAT as the dependent variable. Muscle tissue CSA and abdominal circumference were the common independent variables across groups to explain the variability of the %IntraMAT. It was also extracted %body fat and age for Group 2, age, handgrip strength, and BMI for Group 3, and smoking category for Group 4. These results suggested that muscle tissue size and abdominal circumference would be the strong predictors to explain %IntraMAT of the trunk muscle across four groups, and that age, %body fat, BMI, and SCAT, handgrip strength and smoking category were also good predictors for each group with different exercise frequency in middle-aged Japanese men.