What is underwater weighing

A more simple set up may include a chair and scale suspended from a diving board over a pool or hot tub. Perform screening of health risks and obtain informed consent. Prepare forms and record basic information such as age, height, body weight, gender. See more details of pre-test procedures. The subject, in minimal clothing, then sits on a specialized seat, expels all the air from their lungs, and is lowered into the tank until all body parts are emerged.

The person must remain motionless underwater while the underwater weight is recorded. This procedure is repeated several times to get a dependable underwater weight measure. See videos about Hydrostatic Weighing. For more accuracy residual lung volume RV should be physically measured, though there are calculations for RV estimation. The chair will either be lowered further into the water or the individual will be asked to lower their head into the water until their entire body is submerged.

Once submerged, the individual exhales as much air from their lungs as possible by blowing bubbles. The test administrator records the weight when no more air bubbles appear in the water and the individual can then resurface. The test is typically repeated several times and the average of the weights used to minimize errors.

The recorded weight will be plugged into equations that account for any leftover air in the lungs and gastrointestinal tract to calculate body density in water and total body fat percentage. Underwater weighing is considered one of the most accurate forms of measuring body composition. Underwater weighing was once considered the "gold standard" for comparing accuracy and reliability of other body composition measurement methods.

However, with newer technologies available, it's being used less often since it does require special equipment. The individual should also be capable and comfortable expelling air from their lungs and keeping still while submerged underwater.

Underwater weighing is one method for calculating percentages of body fat and lean mass. Although highly accurate, it is not widely available, and therefore, may not be convenient for taking regular weight measurements. Other methods, such as bioelectrical impedance or skinfold measurements, may be more convenient for tracking changes in weight and body composition.

Ana Reisdorf, MS, RD is a freelance health writer and dietitian with 12 years of experience in the field of nutrition.

You can learn more about her at anareisdorf. Many universities offer hydrostatic weight tests for research purposes, and several companies offer testing for the public. Some, such as Body Fat Test , provide a mobile hydrostatic body composition testing service.

The lack of easy access to this testing makes is less than ideal to use, especially since other methods of measurement are widely available. Hydrostatic weighing is considered to be accurate, but there are other technologies being developed that may replace it. One is the Bod Pod, which uses air displacement in much the same way hydrostatic weighing uses water displacement. Another is dual energy X-ray absorptiometry DEXA , which measures bone mineral content as well as estimating body fat and muscle.

Bioelectric impedance body fat monitors are widely available for home use and at health clubs. They use a low voltage electric current to assess body composition. However, these monitors are less accurate than hydrostatic weighing and dependent on several variables.

Using fat calipers is another accessible, easy method. Get exercise tips to make your workouts less work and more fun. Field comparison of body composition techniques: Hydrostatic weighing, skinfold thickness, and bioelectric impedance. J Orthop Sports Phys Ther. Lee SY, Gallagher D. Assessment methods in human body composition. Br J Nutr. Body composition methods: Comparisons and interpretation.

J Diabetes Sci Technol. Body composition measured by dual-energy X-ray absorptiometry half-body scans in obese adults. Obesity Silver Spring. Your Privacy Rights. To change or withdraw your consent choices for VerywellFit. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page.