Underwater Weighing: When should it be used in the wrestling community?

   Alan C. Utter Ph.D., M.P.H., FACSM

One of the most widely used laboratory procedures to assess body composition is underwater weighing. Underwater weighing is considered one of the gold standards in body composition assessment. In this procedure body density is calculated from body volume according to the Archimedes principle of displacement, which states that an object submerged in water is buoyed up by the weight of water displaced. Once body density has been determined, one can then convert this value to percent body fat through some simple calculations.

The protocol requires weighing a person underwater as well as on land (See Figure). The densities of bone and muscle tissues are higher than that of water, while fat is less dense than water. Therefore, a person with more bone and muscle mass will weigh more in water and thus a higher body density and lower body fat. Underwater weighing also requires the measurement of residual lung volume. The residual lung volume is the amount of air left in the lungs after a maximal expiration. Whenever possible, residual lung volume should be measured directly. When a lab estimates residual volume, the underwater percent fat calculation is no more accurate than skinfolds because of the large amounts of error in residual volume estimation formulas.

How well does underwater perform:

Underwater weighing is a very accurate method to determine percent body fat within the wrestling population. Underwater weighing is usually the validation method in which other body composition methods are compared to in determining accuracy. Because underwater weighing requires proper space, special equipment, and trained personnel it is typically only available in University settings or research centers. Most universities will charge somewhere between $10.00 and $30.00 to have the procedure administered. The entire process wil1 take approximately 30 minutes.

 When should it be used in the wrestling community?

Because underwater weighing does require proper space, special equipment, and trained personnel, it is not very practical in regards to testing a large group of wrestlers in a short period of time. The most common use of underwater weighing within the wrestling community would be that if a wrestler for some reason wanted to appeal his or her minimal competing weight as determined by another body composition method, they should then consider an appeal process. Many state high athletic associations have allowed underwater weighing to be used in an appeal to the original percent fat calculation as determined by another method such as skinfolds. The NCAA has currently approved both underwater weighing and skinfolds in the assessment of percent body fat and subsequent determinations of minimal wrestling weight.

Underwater weighing is considered the ?Gold Standard? with regards to accuracy in determining percent body fat. The disadvantages of underwater weighing include: traveling to a facility that can perform the test, time, and cost. Underwater weighing should be considered if a wrestler wants to receive a very accurate measure of their body composition or may want to appeal a previous body fat measurement determined form another method. Over the years I have tested hundreds of wrestlers using the underwater weighing technique in our Human Performance Laboratory here at Appalachian State University. Our Human Performance Laboratory does make underwater weighing available to any wrestler, athlete, or individual who may be interested at a cost of $15.00.

Questions or concerns on the enclosed article:
Dr. Alan C. Utter
email:utterac@appstate.edu
phone: 828-262-3094