Echo Intensity As An Index Of Intramuscular Fat In Elderly Women Evaluated By Ultrasonography

Abstract

It is shown that increase in intramuscular fat (IMF) occurs with aging (Sipilä and Suominen 1993) and after reduction of physical activity (Manini et al. 2007). However, IMF accumulation pattern in the lower and upper limb muscles is not well understood in the previous studies. It is reported that the IMF can be evaluated based on echo intensity of ultrasonography (Reimers et al. 1993). PURPOSE: The purpose of this study was to establish the estimation of IMF from an index of the echo intensity, and to examine whether there is a relation to change in muscle thickness with aging. METHODS: A total of 15 physically active aged women (age, 69.1 ± 4.7 yr; height, 152.9 ± 3.6 cm; weight, 54.1 ± 6.0 kg; BMI, 23.1 ± 2.5 kg/m2) participated in this study. To determine thickness and echo intensity of muscle and subcutaneous fat, right-upper arm and thigh were scanned using an ultrasonography. Thickness and echo intensity of the biceps brachii (Bi) and brachialis (Br), rectus femoris (RF) and vastus intermedius (VI) at the anterior (50% of length of the thigh, 50% Lt), vastus lateralis (VL) and VI at the lateral 50% Lt, vastus medialis (VM) at the medial 30% Lt were measured. Subcutaneous fat thickness and echo intensity were measured at the anterior upper arm, the anterior 50% Lt, the lateral 50% Lt and, the medial 30% Lt. Echo intensity in the muscle and subcutaneous fat were calculated based on mean grey scale. RESULTS: Muscle thickness of the RF at the anterior 50% Lt was inversely related to echo intensity of the RF (r = -0.58, p < 0.01). Echo intensity of the subcutaneous fat was inversely related to subcutaneous fat thickness in all the tested sites (upper arm, r = -0.52, p < 0.05, anterior 50% Lt, r = -0.65, p < 0.05; lateral 50% Lt, r = -0.75. p < 0.05, medial 30% Lt, r = -0.71, p<0.01). Echo intensities of the RF and VI at the anterior 50% Lt and, that of the VM at the medial 30% Lt were significantly higher than that of the Bi (all p < 0.001). CONCLUSIONS: From these results, we conclude that thickness as well as echo intensity of muscle and subcutaneous fat could be one of the indices in evaluating characteristics of muscle and subcutaneous fat with aging.