An exploratory study on the associations between changes in echo intensity of trunk skeletal muscle and lifestyle-related factors in young Japanese individuals

<title>Abstract</title> <p> Background The skeletal muscle quality is positively associated with the risk of sarcopenia, cardiometabolic, and insulin resistance. However, it remains unclear whether the association between changes in the skeletal muscle quality and lifestyle-related factors differs between males and females in young individuals. This study aimed to explore the associations between 1-year changes in echo intensity (EI) which is an index of the skeletal muscle quality and lifestyle-related factors such as physical activity and dietary intake in young Japanese individuals. Methods Thirty-four young individuals (18 males, 16 females; body mass index: 20.6 ± 2.0 kg/m ² , 19.6 ± 1.9 kg/m ² ) aged 20–26 years came to our laboratory twice with a 1-year interval. EI, skeletal muscle thickness (MT), and intra-abdominal thickness (IAT) were assessed using B-mode ultrasound imaging. MT and IAT were adjusted by body mass ^1/3 . Physical activity was evaluated using the Global Physical Activity Questionnaire. Dietary intake was assessed using the Brief-type Self-Administered Diet History Questionnaire. Cardiometabolic risk factors were evaluated using brachial-ankle pulse wave velocity and blood parameters, including total cholesterol, high-density lipoprotein cholesterol (HDL-cholesterol), triglycerides, and homoeostasis model assessment index of insulin resistance. Results Changes (%) in trunk EI were significantly negatively correlated with changes in plant protein and carbohydrate intakes in males (r _s = -0.529 and − 0.614). In females, changes in trunk EI were significantly negatively associated with changes in HDL-cholesterol levels (r _s = -0.500). No significant associations were observed with the other variables. Conclusion These results suggest that the relationship between EI and lifestyle-related factors is sex-specific. In particular, dietary intake appears to play a key role in young males: EI was associated with the intake of plant protein and carbohydrates, whereas HDL-cholesterol levels were more relevant in young females. </p>