Test-retest Reliability Of Total Body Volume Derived From A Single 2-dimensional Digital Image

Abstract

Simple, accurate, and cost-effective methods to estimate body composition in field settings are valuable to practitioners and clinicians. An automated smartphone- or tablet-based method of determining body composition from a single 2-dimensional (2D) digital image has recently been developed. However, the test-retest reliability has yet to be determined. PURPOSE: The purpose of this study was to evaluate the test-retest reliability of total body volume (BV) estimated from a single 2D digital image. METHODS: A convenience sample was recruited for this study (n=30, 21.0±3.1 yrs., 86.7% female, 24.8±3.0 kg/m2). Body mass was measured (to the nearest 0.1 kg) with a calibrated digital scale (Tanita BWB-800, Tanita Corporation, Tokyo, Japan). Standing height was measured (to the nearest 0.1 cm) with a stadiometer (SECA 213, Seca Ltd., Hamburg, Germany). Two digital images of each participant were taken from the rear/posterior view using a 12.9 inch, 64g iPad Pro. A paired sample T-test was used to examine differences between BV obtained from the images (BV1, BV2). An Intraclass Correlations Coefficient (ICC) assessed the strength of the association between BV1 and BV2. RESULTS: No differences were observed between BV1 and BV2 (71.2±12.0 L versus 71.1±11.7 L, respectively, p=0.51), with excellent agreement between the two measures (ICC=0.99). CONCLUSIONS: This novel method of acquiring BV produced near-perfect reliability within our small sample. Given the excellent reliability, future research should examine the validity of acquiring body composition from a single 2D digital image using an automated smartphone- or tablet-based application.