Challenging the Testing Protocol of the BOD PODEric Shamus, PhD, DPT, CSCS, Sarah Bengtson, DPT, Sierra Griffin, DPT, CSCS

Ahmed Elokda, PhD, PT, FAACVPR, Liza Malley, BS Department of Rehabilitation Sciences, Florida Gulf Coast University

IntroductionAir displacement plethysmography (ADP) is a method of assessing body compositionutilized since the 1990’s. In roughly 5 to 10 minutes, the BOD POD is capable ofassessing body composition, fat mass versus fat free mass, and it can measure the lungvolume within the intrathoracic cavity. ADP uses gas laws to describe the inverserelationship between pressure and volume in two enclosed chambers. Based onethnicity, it uses either the Siri or Shutte equation to calculate body composition via gaslaws and the volume of air and pressure differences exerted within a confined space.

Literature has shown that the BOD POD is a reliable tool within 1% of the gold standard,hydrostatic weighing, for assessing body composition.

Certain precautions are set in place to standardize the testing environment, as well asthe tested subject. Upon testing day, clients are asked to refrain from eating, drinking,or exercising 3 to 4 hours before BOD POD testing, and are asked to use the restroomprior to testing to eliminate any waste within the body. During the testing session, aswim cap is worn.

It is important to consider whether these external factors affect the ability of the BODPOD to accurately measure body composition.

As per the protocol set forth by LMI, liquids should not be consumed 3 to 4 hours prior,as it may skew the body composition results. The question of how much liquid and byhow much it will skew the results is still lacking in the literature and is yet to bedetermined.

Within the population at large, it may be unrealistic for some groups to refrain fromwater intake for more than four hours.

For this reason, it is necessary to challenge this aspect of the manufacturer's protocol inorder to make BOD POD testing more feasible for a greater number of diverse clients.

Some studies have examined the effects of added content within the BOD POD itself,via holding bottles of water and oil, but none have examined the physical consumptionof water, or post urination and the effects these two variables can have on the endresults of BOD POD testing.

BOD POD Testing Protocol• No eating, drinking, or exercising 3 to 4 hours prior to body

composition testing• Participants are to wear compression garments and a swim

cap• Remove all jewelry and eyeglasses

Additions to Protocol Specific to this study:

• Participants were asked to refrain from urinating 2 hours priorto testing

95% Confidence Interval for

Differenceb

(I) Condition (J) Condition Mean Difference

(I - J)

Std. Error Sig. b Lower Bound Upper Bound

1 2 0.303 0.301 0.322 -0.311 0.917

3 0.228 0.299 0.452 -0.382 0.838

4 -0.728 0.347 0.044 -1.435 -0.021

2 1 -0.303 0.301 0.322 -0.917 0.311

3 -0.075 0.205 0.717 -0.493 0.343

4 -1.031 0.296 0.002 -1.635 -0.427

4 1 0.728 0.347 0.044 0.021 1.435

2 1.031 0.296 0.002 0.427 1.635

3 0.956 0.208 0.000 0.532 1.38

Pairwise Comparisons

Multivariate Tests

Value FHypothesis

df Error df Sig.Partial Eta Squared

Noncent. Parameter

Observed Power

Pillia's Trace 0.408 6.658a 3.000 29.000 0.001 0.408 19.974 .953

Wilks' Lambda 0.592 6.658a 3.000 29.000 0.001 0.408 19.974 .953

Hotelling's Trace 0.689 6.658a 3.000 29.000 0.001 0.408 19.974 .953

Roy's Largest root 0.689 6.658a 3.000 29.000 0.001 0.408 19.974 .953

Pre- Urination Std. Test-RetestWater

Consumption

Power Analysis

1st TestStandard LMI BOD POD protocol, with the addition of not

voiding 2 hours prior to testing

2nd & 3rd TestStandard protocol as set forth by LMI for

BOD POD body composition testing

4th TestSubjects were given a measured amount of

water to consume, 10% of their total body

weight in ounces, with 10 minutes to consume

before final measurement

Statistical Test Sample Size Power Correlation Sig. Level

Correlation 28.870 .80 0.5 0.5

Correlation 32 0.8431 0.5 0.5

Research DesignStandard Protocol

Retest Protocol

Standard Protocol

Pearson Correlation 1 .977**

Sig. (2-tailed) .000

N 32 32

Retest Protocol

Pearson Correlation .977** 1

Sig. (2-tailed) .000

N 32 32

**. Correlation is significant at the 0.01 level (2-tailed).

Pearson Moment Correlations

DiscussionIt is thought that excess fluids in the body will be inappropriately categorized as fat masswhen using the BOD POD for body composition measurements. The LMI protocol requiresparticipants to urinate prior to testing in attempts to remove any excess fluids that mayskew the results of the fat mass versus fat free mass compositions. All participants in thisstudy acknowledged that they followed the no urination for two hours prior to testingrequirement.

The standard pretesting protocol set forth by LMI asks participants to refrain from drinkingfluids four hours prior to BOD POD measurements being taken.

• This study found there to be a highly statistically significant difference between thetest-retest and the post water consumption conditions (p value= 0.002 and 0.000respectively).

Major findings of the Present Study•Breaking protocol for BOD POD testing with the consumption of water resulted in asignificant difference in body composition measurements

•Voiding before testing did not have a significant difference (p = 0.322).• Bladder contents do not play a significant role in body composition

measurements• not misappropriated as fat or fat free mass

•Compared with standard protocol testing, consumption of water provided significantlydifferent results in body composition testing (p = 0.002)

• Consuming 10% of an individuals body weight in fluid ounces of water was foundto have an over estimation of fat mass and an underestimation of fat-free mass

• difference between the test-retest fat mass percentages was 0.2% for males and0.3% for females.

• male participants’ measurement of fat mass on average had a difference of 0.6%and female participants’ fat mass measurements on average had a difference of1.4%

• Since reliability was verified between test-retest measures, this was found to bestatistically significant

References

Fields DA, Hunter GR, Goran MI. Validation of the BOD POD with hydrostatic weighing: influence of body clothing. International journal of obesity. Int J ObesRelat Metab Disord. 2000;24(2): 200-5.

Carvennec M, Fagour C, Adenis-Lamarre E, et al. Body composition of obese subjects by air displacement plethysmography: the influence of hydration. Obesity. 2007;15(1): 78-84.

Siri WE. Body composition from fluid spaces and density: analysis of methods, 1961. Nutrition. 1993;9(5):480-91.