Abstract
Sexual and age-related differences of body composition was analyzed in brachium by X-ray computed tomography. Subjects included 104 normal healthy adults (49 males and 55 females) . The ages of the subjects ranged between 20 and 69. CT images were taken at the proximal third point, center and distal third point of the upper arm. The cross sectional areas of subcutaneous fat, muscular layer, intermuscular connective tissue and bone were measured in each image. For the muscular layer, each muscle was specified and measured. Results were related to sexual and age differences. 1) In males the muscular layer was the largest, followed in order by the subcutaneous fat and bone at all levels. In females, the subcutaneous fat was the largest, and the muscular layer was second. 2) Subcutaneous fat in the males increased in the 50 s and 60 s. The muscular layer of the males tended to decrease with age. On the contrary, subcutaneous fat in females increased with age. 3) At the proximal level in males, the brachial triceps reduced with age and the deltoid muscles reduced more. The female triceps and deltoid muscles showed slight age related changes in size. 4) At the other two levels, though the male triceps decreased remarkably with age, the female triceps did not. These muscles were similar in both sexes in the 60s. 5) The sexual difference in the size of each muscle diminished with the difference in motor activity of both sexes. Intermuscular variation was reduced to difference in the fiber type composition of each muscle.
