Influence of Cotton and Spandex Shorts on Air Displacement Plethysmography Estimates of Percent Body Fat

Abstract

0490 Air displacement plethysmography (ADP) is gaining broad acceptance as an alternative to more traditional body composition methods (i.e. hydrostatic weighing and dual energy X-ray absorptiometry). Several studies have shown that certain types of clothing can affect ADP estimates of body fat. In spite of this evidence, it has become common practice to use clothing schemes that deviate from the manufacturer's recommendation of a tight fitting swimsuit. However, no study has specifically investigated the effect of regular cotton gym shorts and biking shorts on ADP estimates of body fat. PURPOSE: The purpose of this study was to investigate the effect of wearing cotton gym shorts and biking shorts on estimates of body fat. METHODS: Twenty-five healthy adult females, (24.8 ± 5.6 years; 163.4 ± 7.5 cm; 56.9 ± 7.4 kg) had their percent body fat measured by ADP. In random order each subject was tested in the following clothing schemes which were provided by the University of Oklahoma body composition laboratory: 1) a tight fitting swimsuit (the criterion clothing condition – CR); 2) normal cotton gym shorts (GS); and 3) bicycle shorts (BS). All thoracic gas volumes were measured and percent fat (%fat) was determined using the Siri equation. RESULTS: GS %fat (21.3 ± 5.3%) and BS %fat (23.4 ± 5.6%) were significantly lower (P< 0.01) than the CR %fat (25.7 ± 5.4%), with their regressions significantly deviating from the line of identity. GS had an R2 0.98 and an SEE of 1.2%fat, while BS had an R2 of 0.98 and an SEE 1.1%fat. Bland Altman analysis revealed no bias in estimates of percent body fat across the range of body fatness for either GS or BS. CONCLUSION: These results indicate testing in cotton gym shorts or bicycle shorts can result in 2% – 4% under-estimation in percent body fat. Therefore, it is recommended that only a tight fitting swimsuit be worn when using ADP in the assessment of body fat.