Reliability of air displacement plethysmography in a large, heterogeneous sample

Purpose: This study was conducted to deter-mine the reliability of ADP using the Bod Pod (R) in a large, heterogeneous sample. Methods: A total of 980 healthy men and women (30 +/- 15 yr, mean +/- SD) completed two body composition assessments separated by 15-30 min. All testing was done in accordance with the manufacturer's instructions. Results: A significant correlation (r = 0.992, P = 0.001) was found between body density (BD) 1 (1.046 +/- 0.001 kg(.)L(-1); mean +/- SEM) and BD 2 (1.046 +/- 0.001 kg(.)L(-1)). A paired t-test revealed no significant difference between BD I and 2 (P = 0.935). The coefficient of variation (CV) for BD was 0.15%. A significant intraclass correlation coefficient (ICC) was found for BD (ICC = 0.996, P 0.001), and the standard error of measurement (SEM) was 0.001 kg(.)L(-1). Body mass (BM) I and 2 were correlated significantly (r = 0.999, P = 0.001); however, a significant (P = 0.001) decrease was seen from BM 1 (75.510 +/- 0.461 kg) to BM 2 (75.497 +/- 0.461 kg). Body volume (BV) tended to decrease (P = 0.08) from BV 1 (69.900 +/- 0.449 L) to BV 2 (69.884 +/- 0.449 L). Conclusion: ADP using the Bod Pod (R) appears to assess BD reliably; however, the observed CV suggests that multiple trials are necessary to detect small treatment effects.