Applicability of segmental bioelectrical impedance analysis for predicting trunk skeletal muscle volume

This study aimed to investigate the validity of using segmental bioelectrical impedance (BI) analysis for estimating skeletal muscle volume (MV) in the trunk, defined as the body segment from the acromion process to the greater trochanter. Using a magnetic resonance imaging (MRI) method, the trunk MV was determined in 28 men (19 approximately 34 yr), divided into validation (n = 20) and cross-validation (n = 8) groups, and used as a reference (MV(MRI)). For BI measurements of the trunk, the source electrodes were placed at the dorsal surface of the third metacarpal bone of both hands and the dorsal surface of the third metatarsal bone of both feet, and the detector electrodes were placed at the acromion process of both shoulders and the greater trochanter of both femurs. Using this arrangement, the BI values of five parts of the trunk, both sides of the upper region, the middle region, and both sides of the lower region, were obtained and then used to calculate the whole trunk BI value and BI index (BI index(TR)). In the validation group, a simple regression analysis of the relationship between BI index(TR) and MV(MRI) showed a significant correlation between the two variables (r = 0.884, P < 0.05) and produced a prediction equation with a SE of estimation of 1,020.3 cm3 (8.5%). In the validation and cross-validation groups, there were no significant differences between the measured and estimated MV without systematic errors. These findings indicate that the segmental BI analysis employed in the present study can be used to estimate trunk MV.