Because muscle sinks and fat floats, a person with more body fat will weigh less underwater and be more buoyant. Someone with more muscle, meanwhile, will weigh more underwater. In an underwater body composition assessment, a person is first weighed on dry land. Next, the person gets into a large tank of water. While sitting on a special scale, they are lowered underwater and asked to expel all the air from their lungs and remain motionless while the underwater weight is measured.
This procedure is repeated three times and averaged. A special calculation is then used to determine lean weight and fat weight and determine the percentage of body fat.
This method of body composition analysis is considered to be very accurate and is used to judge whether other methods are accurate.
It usually is consistent and so it can be used to measure progress. However, the person administering the test needs to understand the principles and do the calculations correctly. A source of error in the test is the need to get all air out the subject's lungs when weighing underwater, as any air remaining will make them float and throw off the results. This is one reason that three underwater weights are taken.
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. Measurements lasted 3—5 seconds.
Body density was calculated by dividing body mass BM by body volume BV , i. Pearson correlation coefficients were calculated to determine associations between techniques. The Bonferroni adjustment was used to correct for multiple comparisons. Cheerleading position i. Power analysis and linear regression were performed using R version 3.
Linear regression can be performed on approximately 15 to 25 subjects per variable, and analyses have shown that less than 10 subjects per variable can be used with good results 2. No cheerleaders were classified as underweight based on BMI. The primary hypotheses were related to comparison of methods for assessing body composition. This appears consistent since female cheerleaders exhibit lean, muscular physiques similar to those of female track-and-field athletes.
Interestingly, no participants were classified as underweight based on BMI, whereas 3. This suggests that BMI should not be used to assess weight status in female cheerleaders. This may be particularly relevant for the back-spots, who were deceptively lean in this investigation i. The lack of statistical power to conduct analyses in male cheerleaders was a limitation.
While the sample size of 28 female cheerleaders, is small, this study was adequately powered and is consistent in size with body composition studies in other collegiate athletic populations e. Another limitation is the potential influence of hydration status on BIA results 7. Although participants were provided instructions to abstain from exercise, eating, and drinking anything other than water for the 3 hours prior to testing and void their bladder upon arrival to the laboratory, hydration assessments did not occur prior to measurements.
This is the first investigation comparing methods for assessing body composition in collegiate cheerleaders. The findings of this study add to the growing body of evidence concerning body composition testing and its importance in the assessment of athletes. Further, BMI is not a valid tool in this population of lean female athletes due to under-classification of health risk. The authors have no conflicts of interest to disclose. National Center for Biotechnology Information , U.
Int J Exerc Sci. AMY L. Author information Copyright and License information Disclaimer. Copyright notice. This article has been cited by other articles in PMC. Abstract This study compared body composition measurements in lean female athletes. Table 1 Anthropometric measures and body composition measures by cheerleading position. Open in a separate window. Protocol Anthropometric and body composition measurements were conducted according to manufacturer instructions.
Table 2 Associations between BMI and body composition measures. Comparisons are based on Pearson correlation coefficients. Linear Regression Linear regression can be performed on approximately 15 to 25 subjects per variable, and analyses have shown that less than 10 subjects per variable can be used with good results 2.
Also, different people pinch differently, which can alter accuracy. Having the same person do the test may minimize this error. Big-chain health clubs often do not use this method because people may feel uncomfortable being touched by strangers, and touching perceived as inappropriate can lead to lawsuits. The NIR machine then uses this information along with age and activity level to estimate body composition.
While variations of this technique have been used in clinical settings since the s, portable devices that are commercially available have been shown to be less accurate than other methods. References 1. Concurrent validity of the BOD POD and dual energy x-ray absorptiometry techniques for assessing body composition in young women. J Am Diet Assoc. Evaluation of air displacement for assessing body composition of collegiate wrestlers. Med Sci Sports Exerc. Heyward VH. Champagne, Ill.
Essentials of Exercise Physiology.
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