Validity of bioelectrical impedance and ultrasonographic methods for estimating the muscle volume of the upper arm

Abstract

The present study aimed to investigate the validity of bioelectrical impedance and ultrasonographic methods for predicting the muscle volume of the upper arm. Bioelectrical impedance of the right upper arm and the thickness of elbow flexor and extensor muscles were measured from 26 healthy young adult men using a specially designed bioelectrical impedance data acquisition system and brightness-mode ultrasound apparatus, respectively. As reference data, the muscle volume (MV_MRI) of the right upper arm was determined using a magnetic resonance imaging method. The impedance index was calculated as L ²/Z, where L is the upper arm length and Z is the impedance of the shoulder to the elbow. The muscle volume (MV_ULT) was calculated as π·(d/2)²·L, where d is muscle thickness. L ²/Z and MV_ULT were significantly correlated with MV_MRI with correlation coefficients of 0.971 and 0.962, respectively. In these relationships, the standard errors of estimation were 44.2 cm³ (6.3%) for L ²/Z and 50.7 cm³ (7.2%) for MV_ULT. There was no significant difference between the absolute errors of muscle volumes estimated by L ²/Z and MV_ULT: 36.2 (4.8, SEM) cm³ for L ²/Z versus 40.3 (5.8) cm³ for MV_ULT. The present results suggest that both bioelectrical impedance and ultrasonographic methods may be useful for predicting the muscle volume of the upper arm.