title: Validity of near-infrared interactance for estimating relative body fat in female high school gymnasts.
abstract: The present investigation examined the validity of near-infrared interactance (NIR) estimates of relative body fat (% fat) from the Futrex-5000 (F5000), Futrex-5000A (F5000 A), and Futrex-1000 (F1000) instruments. Ninety-eight female high school gymnasts (X age+/-SD = 15.7+/-1.2 yr) participated in this investigation. Subsamples were used to cross-validate the F5000 (n = 52), F5000A (n = 46), and F1000 (n = 89) instruments. The NIR % fat estimates were validated against criterion % fat from underwater weighing (UWW) using the adult conversion constants of Brozek et al. (6) (UWWB) and the female age-specific constants of Lohman (23) (UWWL). The cross-validation statistical analysis included examination of the constant error (CE), standard error of estimate (SEE), r, and total error (TE). In addition, full-model multiple regression analyses were used to predict UWWB or UWWL from body weight (BW) and height (HT). BW and HT were correlated with % fat at R = 0.65-0.70, while the validity coefficients for the NIR instruments ranged from r = 0.40-0.78. The F5000 resulted in nonsignificant CE values (-0.3 % fat vs UWWB and 1.5 % fat vs UWWL; p > 0.008) as well as the lowest TE values (TE = 3.1 % fat vs UWWB and 4.0 % fat vs UWWL). All other NIR estimates of % fat resulted in TE values > or = 6.3 % fat. In addition, for all NIR instruments there were negative correlations for the plots of the CE versus the mean of predicted and criterion (UWWB and UWWL) % fat. Therefore, the present findings indicated that the F5000 provided more accurate estimates of % fat than the F5000A or F1000 instruments, but may underestimate the desired minimal body weight for female gymnasts at the low end of the % fat distribution.
authors.affiliation: University of Nebraska-Lincoln, 68588-0229, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Smith
authors.forename: G O
authors.initials: GO
authors.lastname: Johnson
authors.forename: J R
authors.initials: JR
authors.lastname: Stout
authors.forename: T J
authors.initials: TJ
authors.lastname: Housh
authors.forename: D J
authors.initials: DJ
authors.lastname: Housh
authors.forename: T K
authors.initials: TK
authors.lastname: Evetovich
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000293:Adolescent; D001823:Body Composition; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D005544:Forecasting; D006173:Gymnastics; D006801:Humans; D018482:Muscle, Skeletal / Q000033:anatomy & histology; D012044:Regression Analysis; D015203:Reproducibility of Results; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation / Q000706:statistics & numerical data