Validation of bioelectrical impedance to assess body composition change at altitude

In this study, fat free mass (FFM) and % fat were assessed by multisite, multifrequency bioimpedance analysis (BIA), on divers who took part in the altitude diving research program at Mountain Kackar (3412 m). Impedances were measured from different sites (limbs and trunk) at 5 frequencies using a custom made 4-probe impedance analyzer. Skinfold and circumference measurements were used to determine the correlation with bioimpedance results. At sea level, all measurements and corresponding regression equations showed a good correlation for FFM and % fat. Although, correlation between skinfold and circumference did not change upon exposure to altitude, it decreased for BIA. Besides, BIA can predict fluid compartmental changes whereas in skinfold and circumference measurements local composition changes can be monitored. A combined equation should be used utilizing all three methods for a better prediction.