Hydrostatic weighing with measured residual volume is a valid (accuracy ±1.5% error) and reliable estimation of your body fat and fat-free mass. Hydrostatic weighing (or underwater weighing) involves sitting in a chair suspended from a scale in a tank of warm water. You will be asked to exhale all of the air from your lungs while you are totally immersed underwater, during which your weight is measured. This is done several times in order to ensure accuracy.
Residual Volume:To increase the accuracy of hydrostatic weighing, a residual volume (RV) test is also conducted; this test provides an accurate measurement of the amount of air trapped in the respiratory system once you have exhaled as much air as possible. This test is needed only the first time you have the hydrostatic weighing test and is good for 8 years.
The Bod Pod is method of assessing body composition using air displacement (accuracy ±1 to 3% error). It is a quick, automated, noninvasive measurement process that involves sitting in a small, enclosed machine with a window for up to 5 minutes. This test accommodates most populations including children, obese, elderly, and disabled persons. Note: This method is not accurate for those with facial and/or dense body hair.
This is the quickest and least invasive method of body composition assessment. This technique uses very low electrical currents to determine body fat percentage with reasonable accuracy (±3.5% error) as long as pre-test instructions are followed.
A 3-site skinfold measurement using calipers is used to predict relative body fat and lean mass. Skinfold measurement sites differ between sexes: triceps, suprailiac, and thigh for women; chest, abdomen, and thigh for men. This body composition technique is not as accurate as hydrostatic weighing but still estimates body fat with reasonable accuracy (±3.5% error). It is a good technique to monitor changes over time.