Local universities frequently provide the option to have your body composition tested via hydrostatic (underwater) weighing as it is a valuable exercise for their graduate students plus they make a little money to assist program funding. The information below is taken from a local university website where I reside.
Earlier this year I did it for the first time and had skin caliper testing completed at the same time. It's a very good investment, usually ranging from $25 - $50 per test. The graduate student I worked with spent about 2 hours with me, not only executing the two tests but also offering some sound diet advice. It was a valuable experience which I'll complete again for goal measurement.
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Body Composition
Body composition is the measurement of fat mass and fat free mass in an individual's body. This is usually expressed as a percentage such as 20% body fat. Body composition can be measured several different ways. We generally offer skinfold and underwater (hydrostatic) weighing to estimate body fat.
Underwater (hydrostatic) weighing ($25)
This method is currently the gold standard of estimating body fat. It has an error range of 1-2%. Subjects first undergo a pulmonary volume test on a Collins GS Spirometer using helium dilution to measure residual volume. Residual volume (RV) is usually estimated rather than measured. This is usually the largest source of error in estimating body fat by underwater weighing. The Fitness Center reduces this source of error by measuring RV rather than estimating it. The lung volume test requires subjects to breathe into a machine and then perform a maximal inhalation followed by a maximal exhalation. Subjects are then weighed underwater in a specially designed tank that holds treated and heated water such as in swimming pools. During the underwater weighing procedure subjects are required to exhale as much air as possible while being weighed under water. Subjects must wear a bathing suit for this test.
Skinfold Estimation ($5)
This method is very common for measuring body fat. It has an error range usually between 3-4%. Skinfolds are measured using research grade calipers. The skinfold sites on the body vary depending on the equations used to estimate body fat. The UNO Fitness Center usually uses the Jackson & Pollock equations. The skinfold sites for these equations are listed below. Subjects should wear clothing that allows easy access to the skinfold sites.
