BODY COMPOSITION IN FEMALE ATHLETES

1999 The purpose of this investigation was to determine the reliability and validity of bioelectrical impedance (BIA) and near infrared interactance (NIR) for estimating body composition in female athletes. Dual energy x-ray absorptiometry (DXA) was used as the criterion measure for fat free mass (FFM). Studies were performed on 132 college athletes (age=20.4±1.5 yr). Reliability estimates (repeat and single trial) were 0.987-0.997 for BIA (resistance and reactance) and 0.957-0.980 for NIR (optical densities). Validity of BIA and NIR was assessed by a double cross validation technique. Because correlations were high (r=0.969-0.983), and prediction errors low, a single equation was developed using all 132 subjects for both BIA and NIR. Also, an equation was developed on all subjects using height and weight only. Results from DXA analysis showed FFM =49.5±6.0 kg which corresponded to % body fat (% BF) of 20.4±3.1%. BIA predicted FFM at 49.4±5.9 kg (r=0.981, SEE=1.1, TE=1.1) and NIR prediction was 49.5±5.8 kg (r=0.975, SEE=1.2, TE=1.2). Height and weight alone predicted FFM at 49.4±5.7 kg (r=0.961, SEE=1.6, TE=1.6). When converted to % BF values, prediction errors were ∼1.8% for BIA and NIR and 2.9% for height and weight. Results showed BIA and NIR to be extremely reliable and valid techniques for estimating body composition in college-aged, female athletes.