RELATIONSHIP BETWEEN MUSCLE PROPORTION AND QUANTITY OF EXTREMITIES IN YOUNG JAPANESE WOMEN / 体力科学

ABSTRACT

Recently, a long-term health concern has been identified in young Japanese women. These women have a high percentage of body fat despite a normal shape index indicator such as BMI. This condition is called marked obesity, and shows relative low lean body mass. Using an analogous determination, we investigated low percentage of muscle quantity (LM) in the extremities of young Japanese women (n=156) . The cross-sectional areas of muscle, subcutaneous fat, and bone were measured in the upper arm and thigh using ultrasonography. Extremity shape index (CSA<SUB>t</SUB>/L) was defined as the total extremity cross-sectional area (CSA<SUB>t</SUB>) divided by the length of the limb (L), Percent muscle in each extremity (% MA) was calculated from the ratio of muscle CSA to whole limb CSA. LM was defined as the percentage of muscle in the upper arm or thigh less than 1 SD below average and the limb shape index less than 1 SD above average. Nine of 91 subjects displayed LM for the upper arm. A similar proportion of subjects showed LM for the thigh (15/156) . The muscle mass and strength in the upper arm or thigh were compared between the subjects with LM and non-LM subjects with a similar shape index of extremity. There was a tendency towards lower muscle mass and muscle strength in the subjects with LM. From the same comparison, the subjects with LM showed a greater load on extremity muscles to sustain the body weight (i.e., body weight per unit of upper arm or thigh muscle CSA) . To mitigate the deleterious health consequences of low percent muscle quantity it is recommended that young Japanese women who display such a condition should participate in a resistance-training program.