Relationship between quadriceps echo intensity and functional and morphological characteristics in older men and women

The age-related decrease in human skeletal muscle mass; i.e. sarcopenia, has received much attention, but an age-related increase in the ratio of adipose tissue to muscle tissue has received noticeably less. A few studies have shown that ultrasonographic echo intensity, an index of the adipose-to-muscle ratio, is negatively associated with functional capacity, but the best parameters by which to predict this ratio have not yet been established for older individuals. The purpose of this study was to assess the relationships between quadriceps femoris (QF) echo intensity and demographic, functional and morphological characteristics of older men and women. Sixty-four healthy men (n = 27) and women (n = 37) aged 62-88 years (72.0 ± 5.0 years) participated in this study. The echo intensity and muscle thickness of the QF were calculated using ultrasonography. Sit-up, supine-up, sit-to-stand, 5-m maximal walk and 6-min walk tests were performed. There were no significant differences in QF echo intensity between sexes, but QF echo intensity was significantly correlated with QF muscle thickness. Stepwise multiple regression analysis with QF echo intensity as a dependent variable revealed QF muscle thickness, sit-to-stand test in men and age, and QF muscle thickness and sit-to-stand test in women, to be significant variables. These results suggest that QF echo intensity can be explained by QF muscle thickness, sit-to-stand and/or age in older men and women; however, an “age” effect was present only in men.