The present study aimed to investigate the validity of estimating muscle volume by bioelectrical impedance analysis. Bioelectrical impedance and series cross-sectional images of the forearm, upper arm, lower leg, and thigh on the right side were determined in 22 healthy young adult men using a specially designed bioelectrical impedance acquisition system and magnetic resonance imaging (MRI) method, respectively. The impedance index (L(2)/Z) for every segment, calculated as the ratio of segment length squared to the impedance, was significantly correlated to the muscle volume measured by MRI, with r = 0.902-0.976 (P < 0.05). In these relationships, the SE of estimation was 38.4 cm(3) for the forearm, 40.9 cm(3) for the upper arm, 107.2 cm(3) for the lower leg, and 362.3 cm(3) for the thigh. Moreover, isometric torque developed in elbow flexion or extension and knee flexion or extension was significantly correlated to the L(2)/Z values of the upper arm and thigh, respectively, with correlation coefficients of 0.770-0.937 (P < 0.05), which differed insignificantly from those (0.799-0.958; P < 0.05) in the corresponding relationships with the muscle volume measured by MRI of elbow flexors or extensors and knee flexors or extensors. Thus the present study indicates that bioelectrical impedance analysis may be useful to predict the muscle volume and to investigate possible relations between muscle size and strength capability in a limited segment of the upper and lower limbs.

This study aimed to test the hypothesis that a segmental bioelectrical impedance (BI) analysis can predict whole body skeletal muscle (SM) volume more accurately than a whole body BI analysis. Thirty males (19-34 yr) participated in this study. They were divided into validation (n = 20) and cross-validation groups (n = 10). The BI values were obtained using two methods: whole body BI analysis, which determines impedance between the wrist and ankle; and segmental BI analysis, which determines the impedance of every body segment in both sides of the upper arm, lower arm, upper leg and lower leg, and five parts of the trunk. Using a magnetic resonance imaging method, whole body SM volume was determined as a reference (SMV(MRI)). Simple and multiple regression analyses were applied to (length)(2)/Z (BI index) for the whole body and for every body segment, respectively, to develop the prediction equations of SMV(MRI). In the validation group, there were no significant differences between the measured and estimated SMV and no systematic errors in either BI analysis. In the cross-validation group, the whole body BI analysis produced systematic errors and resulted in the overestimation of SMV(MRI), but the segmental BI analysis was cross-validated. In the pooled data, the segmental BI analysis produced a prediction equation, which involves the BI indexes of the trunk and upper thigh as independent variables, with a SE of estimation of 1,693.8 cm(3) (6.1%). Thus the findings obtained here indicated that the segmental BI analysis is superior to the whole body BI analysis for estimating SMV(MRI).

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.

This study tested the hypothesis that, as compared to whole-body bioelectrical impedance (BI) analysis, segmental BI analysis can estimate lean body mass (LBM) more accurately in a population with a large difference in muscularity. In addition to whole-body BI, which determines impedance (Z) between the wrist and ankle, two segmental BI analyses which determine the Z value of every body segment in each of (1) the arms, legs and trunk (distal BI) and (2) the upper arms, upper legs and trunk (proximal BI) were applied to a group of 125 male athletes and 75 non-athletes. The subjects were divided into validation and cross-validation groups. Simple and multiple regression analyses were applied to (length)(2)/Z (BI index) values for the whole-body and each body segment, to develop the prediction equations of LBM measured using air-displacement plethysmography. In the validation group, the SE of estimation was similar in the whole-body (3.4 kg, 5.4%), distal (3.4 kg, 5.5%) and proximal BI (3.3 kg, 5.2%) analyses. However, the whole-body and distal BI analyses produced systematical errors in the estimates of LBM. Moreover, the residuals in the two methods significantly (P < 0.05) correlated with the ratios of BI indices of the upper arms and upper legs to those of the arms and legs, respectively, calculated as variables approximating the relative development of lean tissues at the proximal area of limbs. On the other hand, the proximal BI analysis was validated and cross-validated. Thus, the accuracy of estimating LBM was similar in the whole-body and the two segmental BI analyses. However, the prediction equations derived from the use of the whole-body BI index and a combination of the arms, legs and trunk BI indices produced a systematical error relating to the difference between the limb segments in lean tissue development.

Bioelectrical impedance analysis (BIA) is an affordable, non-invasive, easy-to-operate, and fast alternative method to assess body composition. However, BIA tends to overestimate the percent body fat (%BF) in lean elderly and underestimate %BF in obese elderly people. This study examined whether proximal electrode placement eliminates this problem. Forty-two elderly men and women (64-96 years) who had a wide range of BMI [22.4 +/- 3.3 kg/m(2) (mean +/- SD), range 16.8-33.9 kg/m(2)] and %BF (11.3-44.8%) participated in this study. Using (2)H and (18)O dilutions as the criterion for measuring total body water (TBW), we compared various BIA electrode placements; wrist-to-ankle, arm-to-arm, leg-to-leg, elbow-to-knee, five- and nine-segment models, and the combination of distal (wrists or ankles) and proximal (elbows or knees) electrodes. TBW was most strongly correlated with the square height divided by the impedance between the knees and elbows (H(2)/Z (proximal); r = 0.965, P < 0.001). In the wrist-to-ankle, arm-to-arm, leg-to-leg, and five-segment models, we observed systematic errors associated with %BF (P < 0.05). After including the impedance ratio of the proximal to distal segments (P/D) as an independent variable, none of the BIA methods examined showed any systematic bias against %BF. In addition, all methods were able to estimate TBW more accurately (e.g., in the wrist-to-ankle model, from R(2) = 0.90, SEE = 1.69 kg to R(2) = 0.94, SEE = 1.30 kg). The results suggest that BIA using distal electrodes alone tends to overestimate TBW in obese and underestimate TBW in lean subjects, while proximal electrodes improve the accuracy of body composition measurements.