Author(s): OHTA, M., Institution: CHUKYO UNIVERSITY, Country: JAPAN, Abstract-ID: 723

INTRODUCTION:
The quantity and quality of skeletal muscle have been shown to be associated with sarcopenia, diabetes, and heart disease. Muscle mass (MM) decreases with aging and physical inactivity but can be increased through appropriate training. On the other hand, echo intensity (EI), one index for evaluating muscle quality, is known to increase with aging and physical inactivity and to decrease with training. Nonetheless, the specific relationship between muscle quality and physical function or exercise habits has not been sufficiently examined., and furthermore, few studies have simultaneously investigated muscle quantity and quality in women. Thus, this study collected data on muscle quantity, muscle quality, physical function, and exercise habits in young women with the aims of 1) examining the relationships between these variables and 2) investigating the influence of exercise habits.
METHODS:
Participants were 21 women aged 30-46 years. Whole-body and segmental MM was measured using a body composition analyzer, and MM per weight (MM/W) was calculated. EI of the rectus femoris was calculated from ultrasound cross-sectional images of the anterior thigh and corrected by subcutaneous fat thickness. Physical function measures were assessed as muscle strength, agility, jumping ability, and aerobic capacity. After performing correlation analysis between variables, participants were divided into two groups based on exercise duration since adolescence: the long exercise history (LEH group, n = 9) with 132 months or more of exercise, and the short exercise history (SEH group, n = 12) with less than 60 months. Then, intergroup differences were examined.
RESULTS:
EI showed a negative correlation with MM/W (r = -0.472, p = 0.031) and a positive correlation with % body fat (r = 0.575, p = 0.006). MM/W showed positive correlations with grip strength, agility, and jumping ability (r = 0.451-0.719, p = 0.000-0.046). EI showed a negative correlation with agility, jumping ability, and aerobic capacity (r = -0.454--0.566, p = 0.009-0.039). Furthermore, a longer duration of exercise participation since adolescence was associated with greater MM/W in the upper limbs, lower limbs, and trunk, as well as higher grip strength, agility, and aerobic capacity (p = 0.000-0.025). Comparing the LEH and SHE groups revealed that the LEH group had higher MM/W, greater grip strength, agility, jumping ability, and aerobic capacity, and lower EI (p = 0.000-0.043).
CONCLUSION:
EI showed a negative correlation with MM/V and a positive correlation with %body fat, consistent with previous studies. Furthermore, incorporating muscle quality as a factor alongside MM could more effectively explain physical function. Although the exercise experienced by participants in this study varied, it became clear that long-term exercise, regardless of the type of exercise, has a positive effect not only on MM and physical function but also on muscle quality.