Comparison of Bioimpedance and Underwater Weighing Body Fat Percentage Before and Acutely After Exercise at Varying Intensities.

Nickerson, BS, Esco, MR, Kliszczewicz, BM, and Freeborn, TJ. Comparison of bioimpedance and underwater weighing body fat percentage before and acutely after exercise at varying intensities. J Strength Cond Res 31(5): 1395-1402, 2017-The purpose of this study was to compare single-frequency bioelectrical impedance analysis (BIA) and bioimpedance spectroscopy (BIS) with underwater weighing (UWW) body fat percentage (BF%) before (PRE), immediately post (IP), and 60 minutes post (60P) an acute bout of moderate and vigorous aerobic exercise. Nine men (age = 24.6 ± 3.7 years) volunteered for this study. Subjects visited the laboratory on 3 separate occasions. Testing included two 30-minute exercise sessions at 60 and 80% heart rate reserve (HRR) and a 30-minute control (CON) trial. The constant error (CE) was significantly higher for BIA at each time point and exercise session (CE = 3.0-4.9% for 60% HRR; 2.5-4.7% for 80% HRR). Conversely, BIS yielded a nonsignificant CE at each time point and exercise session (CE = -0.9 to 1.1% for 60% HRR; -0.3 to 1.2% for 80% HRR). The standard error of estimate (SEE) for both exercise sessions ranged from 2.7 to 3.1% and 3.8-4.3% for BIA and BIS, respectively. The 95% limits of agreement were narrower for BIA (60% HRR = ±5.5 to 7.8%; 80% HRR = ±6.6 to 8.5%) than BIS (60% HRR = ±8.4 to 9.4%; 80% HRR = ±8.1 to 10.2%). Results indicate that BIS can be used for mean group BF% in men at PRE, IP, and 60P time periods. However, BIA yielded a lower SEE and 95% limits of agreement than BIS. Therefore, BIA provides better individual estimates of BF% in men, but the CE should be taken into consideration.