Assessment of body composition by bioelectrical impedance analysis. Influence of electrode placement / 体力科学

ABSTRACT

In previous assessments of body composition by whole body bioelectrical impedance (BI) analysis, electrodes have almost always been placed on the right side of the body. In fact, the most commonly used equations of Lukaski et al, were developed using BI measurements obtained on the right side of the body. However, in some individuals with traumatic injury or orthopedic problems, it would sometimes be necessary to measure BI on the right left side of the body. In the present study, we investigated the effects of electrode placement on BI and the derived percentage body fat. Subjects were 72 nontrained, healthy adult women age ; 28.1±12.6 yr (1866), height ; 156.3±6.0cm, weight ; 50.5±7.7 kg, percentage body fat ; 24.4±5.2%. BI was measured for each subject in a supine position by use of a Selco SIF-881 plethysmograph (800 μA, 50 kHz) and ECG electrodes (Nikon Kohden) . The tetrapolar configuration was adopted in order to minimize contact impedance or skin-electrode interation. Eating and exercise were prohibited for at least 3 h prior to assessment. The effects of electrode placement were determined under four conditions 1) the right arm and right leg (R side), 2) the right arm and left leg (R side-L side), 3) the left arm and right leg (L side-R side), 4) the left arm and left leg (L side) . Body density was predicted from the equation developed by Nagamine et al., and percentage body fat was derived from the body density according to Brozek et al. There were significant differences in BI values among the four conditions. Dominant side BI values were significantly lower than those on the non-dominant side. Percentage body fat values estimated under four different BI test conditions (i, e., R, R-L, L-R, and L) in terms of electrode placement were found to be highly correlated (r= 0.9420-0.956) with hydrodensitometrically determined percentage body fat. However, the mean percentage body fat on the dominant side of the body were significantly lower than that on the non-dominant side. We suggest that electrodes can be placed either on the dominant side or on the non-dominant side of the body for normal individuals, assuming that the lowest value from the four combinations of measurements can be used as the criterion value of BI. When the subjects are athletes, BI values obtained on the dominant side or a mean of the values measured on both sides should be adopted.