Purpose: The purpose of this study was to test the convergent validity of Omron 306 using Biospace InBody 720.
Method: A total of 267 participants (145 boys; aged 10.4-17.9 years) completed testing during a single session. Each measure provided percent body fat (%BF), while the InBody 720 included fat-free mass (FFM). The validity was examined using the Pearson correlation. Limits of agreement (LOA) and multiple linear regression were also used to determine the impact of both age and FFM on the associations between the 2 measures.
Results: The 2 measures of %BF were correlated by .63 (p < .001) in boys and .89 (p < .001) in girls. The mean difference (i.e., InBody - Omron) for %BF in boys was - 4.7% with a lower LOA of - 20.5% and upper LOA of 11.2%. The same comparison for girls resulted in a difference of 3.0% with a lower LOA of - 10% and upper LOA of 4%. Examination of the residuals obtained from multiple linear regression indicated that FFM was the only statistically significant predictor of differences in boys (βFFM = - 0.25 ± 0.08%, p = .001). There were no significant associations for girls.
Conclusions: Findings indicate that estimates of %BF obtained from Omron in boys exceed estimates from InBody 720. Disagreement was evident in younger boys with lower levels of FFM. Girls' %BF was closer between the 2 bioelectrical impedance analyzer measures (less residual) with age and FFM not explaining the disagreement. Overall, the 2 measures were not equivalent.
Keywords: body fat; fitness; measurement; youth.