The use of actual, predicted and constant residual volumes in the assessment of body composition by underwater weighing

An attempt has been made to evaluate the extent of the potential error inherent in using either a constant average value or a predicted value of residual volume as opposed to the actual measurement of residual volume in the calculation of body density, percent body Fat and lean body weight. Measurements of underwater weight, residual volume and vital capacity were recorded from 69 male and 128 female college age subjects. The results indicate a very close agreement between the actual values for density, percent fat and lean body weight, and those obtained through either an estimated or a constant residual volume. There is, however, enough individual variation to indicate the necessity for using the actual measured residual volume for research purposes when absolute accuracy is essential.