title: Reliability and concurrent validity of Futrex and bioelectrical impedance.
abstract: Thirty Caucasian males (aged 19-32yr) participated in this study designed to investigate the reliability of multiple bioelectrical impedance analysis (BIA) and near-infrared spectroscopy (Futrex, FTX) measurements and the validity of BIA and FTX estimations of hydrostatically (UW) determined percent body fat (%BF). Two BIA and two FTX instruments were used to make 6 measurements each of resistance (R) and optical density (OD) respectively over a 30 min period on two consecutive days. Repeated measures ANOVA indicated that FTX and BIA, using manufacturer's equations, significantly (p<0.01) under predicted UW by 2.4 and 3.8%BF respectively. Standard error of estimate (SEE) and total error (TE) terms provided by regression analysis for FTX (4.6 and 5.31%BF respectively) and BIA (5.65 and 6.95%BF, respectively) were high. Dependent t-tests revealed no significant differences in either FTX or BIA predictions of %BF using two machines. Intraclass reliabilities for BIA and FTX estimates of UW %BF across trials, days, and machines all exceeded 0.97. A significant random error term associated with FTX and a significant subject-by-day interaction associated with BIA was revealed using the generalizability model. Although FTX and BIA estimates of UW %BF were reliable, due to the significant underestimation of UW %BF and high SEE and TE, neither FTX nor BIA were considered valid estimates of hydrostatically determined %BF.
authors.affiliation: Texas Children's Hospital Wellness Center, Baylor College of Medicine, Houston 77030, USA. pverhs@msmail.is5.tch.tmc.edv
authors.forename: P
authors.initials: P
authors.lastname: Vehrs
authors.forename: J R
authors.initials: JR
authors.lastname: Morrow
authors.forename: N
authors.initials: N
authors.lastname: Butte
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001823:Body Composition; D017097:Electric Impedance; D006801:Humans; D008297:Male; D012044:Regression Analysis; D015203:Reproducibility of Results; D019265:Spectroscopy, Near-Infrared