Hydrostatic weighing: Difference between revisions
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* Metric: RV-Est(Women) = 1.812 X Ht. (meters) + 0.016 X Age (yrs.) - 2.003 |
* Metric: RV-Est(Women) = 1.812 X Ht. (meters) + 0.016 X Age (yrs.) - 2.003 |
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[[Lung volumes|Residual volume]] may also be estimated as a proportion of [[vital capacity]] (0.24 for men and 0.28 for women).<ref>{{cite journal | author = Wilmore, J. H. | title = The use of actual predicted and constant residual volumes in the assessment of body composition by underwater weighing | journal = Med Sci Sports | year = 1969 | volume = 1 | pages = 87–90 | doi=10.1249/00005768-196906000-00006}}</ref> |
[[Lung volumes|Residual volume]] may also be estimated as a proportion of [[vital capacity]] (0.24 for men and 0.28 for women).<ref>{{cite journal | author = Wilmore, J. H. | title = The use of actual predicted and constant residual volumes in the assessment of body composition by underwater weighing | journal = Med Sci Sports | year = 1969 | volume = 1 | issue = 2 | pages = 87–90 | doi=10.1249/00005768-196906000-00006}}</ref> |
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==Application== |
==Application== |
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Once body density has been calculated from the data obtained by hydrostatic/underwater weighing, [[body composition]] can be estimated. The most commonly used equations for estimating the percent of body fat from density are those of Siri<ref name="siri">{{citation | author = Siri, SE | chapter = Body composition from fluid spaces and density: analysis of methods |veditors= Brozek J, Henschel A | title = Techniques for measuring body composition | location = Washington, DC | publisher = [[United States National Academy of Sciences|National Academy of Sciences]], [[United States National Research Council|National Research Council]] | year = 1961 | pages = 223–34 }}</ref> and Brozek et al.:<ref name="brozek">{{citation | vauthors = Brozek J, Grande F, Anderson JT, Keys A | title = Densitometric Analysis of Body Composition: Revision of some Quantitative Assumptions | journal = Ann. N. Y. Acad. Sci. | volume = 110 | pages = 113–40 | date = September 1963 | pmid = 14062375 | doi = 10.1111/j.1749-6632.1963.tb17079.x }}</ref> |
Once body density has been calculated from the data obtained by hydrostatic/underwater weighing, [[body composition]] can be estimated. The most commonly used equations for estimating the percent of body fat from density are those of Siri<ref name="siri">{{citation | author = Siri, SE | chapter = Body composition from fluid spaces and density: analysis of methods |veditors= Brozek J, Henschel A | title = Techniques for measuring body composition | location = Washington, DC | publisher = [[United States National Academy of Sciences|National Academy of Sciences]], [[United States National Research Council|National Research Council]] | year = 1961 | pages = 223–34 }}</ref> and Brozek et al.:<ref name="brozek">{{citation | vauthors = Brozek J, Grande F, Anderson JT, Keys A | title = Densitometric Analysis of Body Composition: Revision of some Quantitative Assumptions | journal = Ann. N. Y. Acad. Sci. | volume = 110 | pages = 113–40 | date = September 1963 | pmid = 14062375 | doi = 10.1111/j.1749-6632.1963.tb17079.x | s2cid = 2191337 }}</ref> |
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Siri (1956): Fat % = [4.950 /Density - 4.500]×100 |
Siri (1956): Fat % = [4.950 /Density - 4.500]×100 |
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Revision as of 20:29, 8 July 2022
 | This article needs additional citations for verification. (June 2011) |
Hydrostatic weighing, also referred to as "underwater weighing", "hydrostatic body composition analysis", and "hydrodensitometry" is a technique for measuring the density of a living person's body. It is a direct application of Archimedes' principle, that an object displaces its own volume of water.
Method
The procedure is based on Archimedes' principle, which states that: The buoyant force which water exerts on an immersed object is equal to the weight of water that the object displaces.
Example 1: If a block of solid stone weighs 3 kilograms on dry land and 2 kilogram when immersed in a tub of water, then it has displaced 1 kilogram of water. Since 1 liter of water weighs 1 kilogram (at 4 °C), it follows that the volume of the block is 1 liter and the density (mass/volume) of the stone is 3 kilograms/liter.
Example 2: Consider a larger block of the same stone material as in Example 1 but with a 1-liter cavity inside of the same amount of stone. The block would still weigh 3 kilograms on dry land (ignoring the weight of air in the cavity) but it would now displace 2 liters of water so its immersed weight would be only 1 kilogram (at 4 °C).
In either of the examples above, the correct density can be calculated by the following equation:
Where: Db = Density of the body, Ma = "Mass in air" (i.e. dry weight), Mw = "Mass in water" (i.e. underwater weight), Dw = Density of water (based on water temperature), RV = Residual volume (the unfilled space enclosed by the body- e.g. volume of air in the lungs + respiratory passages after a maximum exhalation).
The residual volume in the lungs can add error if not measured directly or estimated accurately. Residual volume can be measured by gas dilution procedures or estimated from a person's age and height:[1]
- Inches: RV-Est(Men) = 0.033 X Ht. (inches) + 0.022 X Age (yrs.) - 1.232
- Metric: RV-Est(Men) = 1.310 X Ht. (meters) + 0.022 X Age (yrs.) - 1.232
- Inches: RV-Est(Women) = 0.046 X Ht. (inches) + 0.016 X Age (yrs.) - 2.003
- Metric: RV-Est(Women) = 1.812 X Ht. (meters) + 0.016 X Age (yrs.) - 2.003
Residual volume may also be estimated as a proportion of vital capacity (0.24 for men and 0.28 for women).[2]
Application
Once body density has been calculated from the data obtained by hydrostatic/underwater weighing, body composition can be estimated. The most commonly used equations for estimating the percent of body fat from density are those of Siri[3] and Brozek et al.:[4]
Siri (1956): Fat % = [4.950 /Density - 4.500]×100
Brozek et al. (1963): Fat % = [4.570 /Density - 4.142]×100
References
- ^ Quanjer P.H., Ed. (1983). "Standardized Lung Function Testing". European Community for Coal and Steel, Luxembourg.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Wilmore, J. H. (1969). "The use of actual predicted and constant residual volumes in the assessment of body composition by underwater weighing". Med Sci Sports. 1 (2): 87–90. doi:10.1249/00005768-196906000-00006.
- ^ Siri, SE (1961), "Body composition from fluid spaces and density: analysis of methods", in Brozek J, Henschel A (eds.), Techniques for measuring body composition, Washington, DC: National Academy of Sciences, National Research Council, pp. 223–34
- ^ Brozek J, Grande F, Anderson JT, Keys A (September 1963), "Densitometric Analysis of Body Composition: Revision of some Quantitative Assumptions", Ann. N. Y. Acad. Sci., 110: 113–40, doi:10.1111/j.1749-6632.1963.tb17079.x, PMID 14062375, S2CID 2191337