Inter Instrument Reliability of Body Composition Measures Using Air Plethysmography Methods

Abstract

PURPOSE: The purpose of this study was to determine the inter instrument reliability of body composition measures using air displacement plethysmography as determined by two separate LMI Bod Pod units. METHODS: The study consisted of 147 (59 females, 88 males) subjects whose body composition was measured in each of two LMI Bod Pod Air Plethysmography units during a single visit. The subjects wore tight fitting clothing (swimsuits or leotard) and a swimming cap to reduce the effects of clothing on the measures. Height was measured using a standard Accustat stadiometer immediately preceding the two tests. The subjects were randomly assigned to one of the Bod Pod Units for an initial body composition measure. Upon completion of the initial measure, they were immediately tested for a second body composition measure using the other Bod Pod. Weight was determined for each test using the calibrated digital scale supplied with each of the Bod Pods. Predicted tidal gas volumes of the lung were used to adjust density measures for residual lung volumes for each of the tests. RESULTS: Data analysis was completed using repeated measures ANOVA to determine an intraclass correlation coefficient for body composition and weight. The mean age of the subjects was 32.89 years. The mean height of the subjects was 171.602 cm. The mean weight for both Bod Pod measures was 79.29 kg. The repeated measures for weight yielded an R value equal to 0.999, and the repeated measures analysis for body composition yielded an R value of 0.978. The reported R values for both weight and body composition were significant at the p<.05 level. CONCLUSIONS: The results of this study confirm that air displacement plethysmography measures independent of a specific Bod Pod instrument are reliable and reproducible when determining body composition measures.