Convergent Validity of Skinfold Thickness and the Hand-held Bioelectrical Impedance Analyzer using Current FITNESSGRAM Standards

Given the limitations of BMI, low-cost alternatives are needed to accurately and efficiently estimate adiposity in physical education classes. The purpose of this study was to examine the convergent validity between the Omron HBF-301 BIA device (BIA) and skinfold thickness assessment (SKF) in middle-school students using current FITNESSGRAM standards. Body composition was assessed on 134 students from the 6-8 grades. SKF consisted of averaging three skinfolds measurements at two sites (tricep, calf) using gender-specific Slaughter equations to estimate percent body fat (%BF). BIA required entering physical characteristics into the analyzer then having students hold the device until a %BF reading was displayed. Correlations between SKF and BIA were (r=.72, P<.001) with a 3.81% pred iction error between methods. Bland-Altman plots yielded wide Limits of Agreement with a significant trend of r= -.34 (P<.05) for Grade 8. Classifying students into FITNESSGRAM’s Fitness Zones, a modified kappa coefficient of .48 (95% CI: .35, .66; P<.001) and proportion of agreement o f 0.83 was found between methods. The results suggest although BIA and SKF classified youth into Fitness Zones similarly, there were large differences in %BF estimat ion between methods with BIA tending to underestimate %BF compared to SKF in older children with higher levels of ad iposity.