Several prediction equations for estimating body composition of Japanese men and women have recently been developed using a linear regression model with a combination of impedance and anthropometric measurements as independent variables. The purpose of this study was to determine the cross-validity of body density (Db) estimated from bioelectrical impedance (BI) and skinfold thickness (ST) methods in comparison with underwater weighing (UW) as a criterion reference method. Percentage body fat (%BF) was derived from Db according to the equation Brozek et al. Fifty-seven healthy Japanese women, aged 19 to 57 years, volunteered to participate in the study. Impedance was measured by use of a portable four-terminal impedance plethysmograph (Selco, SIF-891) . %BF derived from the BI method (r=0.860-0.875) was correlated with hydrodensitometrically determined %BF to a greater extent than %BF obtained using the ST method (r=0.7330.758) or ultrasound method (r=0.536-0.721) . Correlations of various anthropometric indices (r=0.655-0.691) with hydrodensitometrically determined %BF were even lower. It was noteworthy, however, that mean %BF derived from existing BI equations differed significantly from hydrodensitometrically determined mean %BF. Therefore, we attempted to develop a new equation that was applicable to Japanese adult women as follows: Db=1.1613-0.1038 (Wt⋅Z ) /Ht², where Wt=weight in kg, Z=impedance in ohms, and Ht=height in cm. The prediction accuracy of this equation was r=0.866 or SEE=0.0077 g/ml. Cross-validation of this equation on a different sample (122 Japanese women, aged 18 to 59 years) revealed a correlation of r=0.869 in terms of %BF, SEE=3.2%, and no significant difference between estimated %BF and the criterion. We suggest that the BI method is one of the most convenient, valid means of assessing human body composition, and that the newly developed BI equation could be useful particularly when the subjects are Japanese adult women in their late teens to fifties.

A study was conducted to investigate the validity of skinfold-based prediction equations for body density (Db, g/ml) developed by Nagamine et al. (1974), and to formulate convenient, useful equations for predicting Db by the skinfold thickness (ST) method in junior high school boys and girls. The subjects of the study were 269 healthy boys and girls, aged 12-15 years. The dependent variable, Db, was determined by underwater weighing (UW) . Independent variables included single skinfold thickness at three sites (triceps, subscapular and abdomen) and the sum of two skinfolds. Db by the ST method was estimated from the equations developed by Nagamine et al. (1974) for boys and girls, using the sum of skinfold thickness at the triceps and subscapular area. Skinfold thickness was measured on the right side of the body with an Eiken-type skinfold caliper. Db estimated by the ST method was correlated significantly with Db determined by UW (r=0.873 for boys and r=0.723 for girls) . However, average Db values estimated by the ST method were significantly lower than those deter-mined by UW (differences in Db values when predicted by the Nagamine equations: 0.0099 for boys and 0, 0114 for girls) . Therefore, we developed linear regression equations for predicting Db. The best-fitting prediction equation for Db was Db=1.0881-0.0010·X for boys, and Db=1.0715-0.0007·X for girls, where X is the sum of the triceps and subscapular skinfold thickness (mm) for boys and girls. Db estimated from the respective equation was correlated significantly with hydrodensitometrically determined Db (r=0.872, SEE=0.0089 for boys; r=0.722, SEE=0.0104 for girls) .
Furthermore, in a cross-validation analysis of prediction equations for Db developed in the present study, Db estimated from the respective equation was correlated highly with hydrodensitometrically determined Db (r=0.887 for boys and r=0.740 for girls) . There were no significant differences between the Db values predicted by the ST method against hydrodensitometrically determined Db values (difference values: 0.0012 for boys and 0.0013 for girls) . The final phase of this study was to develop more stable equations, combining validation and cross-validation samples. On the basis of the final analyses, we recommend the equations Y=1.0875-0.0010X and Y=1.0716-0.0007X, with SEE of 0.0088g/ml for boys and 0.0105g/ml for girls, respectively. It is suggested that the prediction equations finally developed in the present study will be applicable to junior high school boys and girls.

The tetrapolar bioelectrical impedance (BI) method has been proposed as a convenient, valid approach for estimating the body composition of normal healthy adults. However, the validity of the BI method has not yet been confirmed for Japanese junior high school boys and girls. The purpose of this study was to develop convenient and useful equations for predicting the body composition in junior high school boys and girls by the BI method. The subjects were 297 healthy boys and girls, aged 12.15 years, all of whom were Japanese. Impedance was measured using a tetrapolar bioelectrical impedance plethysmograph (800 pA, 50 kHz SIF-891) manufactured by Selco. Multiple regression analysis was used to derive prediction equations for Db that were specifically applicable to boys and girls. The effective prediction equations for Db were as follows : 1) Db=1.1860-0.1282 (Wt·Z) /Ht², and 2) Db=1.1402-0.0706 (Wt·Z) /Ht²-0.0007· (abdomen) for boys. 1) Db=1.1337-0.0778 (Wt·Z) /Ht², and 2) Db=1.1124-0.0498 (Wt·Z) /Ht²-0.0006· (subscapular) for girls, where Db=body density (g/ml), Wt=weight (kg), Z =impedance (ohms), Ht=height (cm) . Db estimated by each respective equation was highly correlated with body density measured by underwater weighing (UW-Db) : 1) r=0.881, SEE=0.00868/ml, 2) r=0.902, SEE=0.00788/nil for boys and 1) r= 0.741, SEE=0.0101 g/ml, 2) r=0.775, SEE =0.0095g/ml for girls. Furthermore, in a cross-validation analysis of prediction equations for Db, another sample consisting of 40 boys and 66 girls was used. Db estimated from each respective equation was correlated highly with UW-Db : 1) r=0.856, 2) r=0.887 for boys and 1) r=0.837, 2) r=0.860 for girls. There were no significant differences between the mean Db obtained by the BI method and that by the criterion method. We suggest that the prediction equations proposed in this study are useful for valid assessment of body composition of Japanese junior high school boys and girls aged 12 through 15 years.

Objective：We aimed to examine the criterion-related validity of observable items of gait abnormality in patients with knee osteoarthritis (OA) using three-dimensional gait analysis and to assess the test-retest reliability.Methods：The items of gait abnormality were pooled from a prior study and rated using a 3-point scale. Content validity was examined by four experts in knee OA research and accepted when there was an agreement among at least three experts. Correlation between abnormality rating and three-dimensional gait analysis data was examined. The test-retest reliability of the agreement rate was then assessed in the same subject twice.Results：Eleven items were pooled, and all met the criterion of content validity. Eight items showed adequate correlation with the three-dimensional gait analysis data and had test-retest reliability exceeding 0.61.Conclusion：In patients with knee OA, observable items of gait abnormality had good test-retest reliability and criterion-related validity according to the three-dimensional gait analysis data.

Objective：We aimed to examine the criterion-related validity of observable items of gait abnormality in patients with knee osteoarthritis (OA) using three-dimensional gait analysis and to assess the test-retest reliability.Methods：The items of gait abnormality were pooled from a prior study and rated using a 3-point scale. Content validity was examined by four experts in knee OA research and accepted when there was an agreement among at least three experts. Correlation between abnormality rating and three-dimensional gait analysis data was examined. The test-retest reliability of the agreement rate was then assessed in the same subject twice.Results：Eleven items were pooled, and all met the criterion of content validity. Eight items showed adequate correlation with the three-dimensional gait analysis data and had test-retest reliability exceeding 0.61.Conclusion：In patients with knee OA, observable items of gait abnormality had good test-retest reliability and criterion-related validity according to the three-dimensional gait analysis data.