DERIVATION OF PREDICTION EQUATIONS FOR RV IN OVERWEIGHT MEN AND WOMEN

Purpose: The purpose of this research was to derive and compare regres sion equations for predicting residual volume (RV) in overweight and n ormal weight adults. Methods: RV was determined on land, in 311 men an d women, following an overnight fast, using the nitrogen-dilution tech nique. Subjects were then weighed underwater at RV; 5-10 underwater we ights were recorded; an the heaviest 3 measurements were averaged as t he underwater weight. Percent body fat was calculated using the Siri e quation. Group analyses were performed on overweight men (N = 59, body fat > 25%) and women (N = 126, body fat > 30%) compared with normal w eight men (N = 68, body fat less than or equal to 25%) and women (N = 58, body fat less than or equal to 30). A stepwise regression was perf ormed for each group using the Systat Statistical Package (Evanston, I L). Results: When RV was regressed on sex, age (yr), body weight (kg), and height (cm), sex was not found to be a significant predictor vari able for RV. Subsequent regressions revealed that prediction equations for the overweight (RV = 0.0277 AGE + 0.0048 WT + 0.0138 HT -2.3967, F = 44.0, P < 0.0000, SEE = 0.405) were different from those generated for normal weight men and women (RV = 0.0275 AGE + 0.0189 HT -2.6139, F = 58.6, P < 0.0000, SEE = 0.405). Similar equations were obtained w hen a cross validation was performed on a separate sample of normal we ight (N = 31) and overweight (N = 46) men and women. Conclusion: These data suggest that prediction equations for RV are separate and distin ct for the overweight and normal weight populations.