Research comparing portable body composition methods, such as bioelectrical impedance analysis (BIA), to air displacement plethysmography (ADP) is limited. We assessed reliability and validity of predicting fat-free mass (FFM) by the RJL, Omron, and Tanita BIA machines using ADP via BodPod as a criterion. FFM (kg) was assessed twice in college students (N = 77, 31 males and 46 females; age = 19.1 ± 1.2 years) using ADP, RJL, Omron, and Tanita BIAs. Reliability was assessed using analysis of variance to obtain an intraclass correlation statistic (Rxx). Validity was assessed using Pearson correlation (r) coefficient. FFM averaged 75.6 ± 9.4 kg in men and 59.8 ± 7.6 kg in women. Reliability was high in both genders RJL (Rxx = .974-.994), Omron (Rxx = .933-.993), and Tanita (Rxx = .921-.991). Validity within males was also high: RJL (r = .935), Omron (r = .942), and Tanita (r = .934), and only slightly lower in females: RJL (r = .924), Omron (r = .897), and Tanita (r = .898). The RJL, Omron, and Tanita BIA machines appear to be both reliable and valid for predicting FFM of male and female college students. Therefore, any of these three BIA devices is appropriate to use for body composition assessment in a healthy adult population.
Keywords: body composition measurement; concurrent validity; test–retest reliability.