The Estimation of the Fat Free Mass Index in Athletes

Purpose: the purpose of this investigation was to compare a practical measurement of fat free mass index (ffmi) from bioelectrical impedance analysis (bia) to the dual energy x-ray absorptiometry (dexa) value in collegiate athletes. methods: thirty-three male baseball players and 16 female gymnasts volunteered to participate in this study during their respective pre-season. subjects visited the laboratory once and had their measurements taken in the following order: weight, height, dexa, and omron hbf-500. results: the bia device investigated was not a valid estimate of ffmi when compared to the dexa. the te was 0.93 kg/ m2 for males and 0.78 kg/ m² for females. there were also significant mean differences between the bia prediction and the dexa value for males (bia=20.6 kg/m² vs. dexa=21.1 kg/m², p=0.007) and females (bia=16.2 kg/m² vs. dexa=17.5 kg/m², p=0.001). conclusions: the bia device investigated in this study did not provide a valid estimate of ffmi in male and female collegiate athletes. although there was a general tendency for the bia to underestimate ffmi compared to dexa, 98% of the estimates were within plus or minus 2 kg/ m². therefore, while slightly biased, bia may provide a reasonable (± 2 kg/ m²) estimate of nutritional status for practitioners who are unable able to afford more expensive equipment.