Bodyfat Percentage - Determining Accurate Bodyfat Easily

Using the Hydrostatic Weighing Method described in Bodyfat - Combating Childhood Obesity Through Motivation
To generate the most precisely accurate Bodyfat Percentage value from our Hydrostatic Weighing Method, it is beneficial to answer the following questions. If they are not answered, the result will be for the adult male pre-selected in the questions!
Are you: . . . . . . . . . . . . . . . Male . . . . . . . . . . . . . . Female
Are you age: . . . . . . . 5-12 . . . . . . . 13-20 . . . . . . . 21-49 . . . . . . . 50 or over
Are you: . . . . . . . Caucasian . . . . . . . Black . . . . . . . Asian
Are you: . . . . . . . Average Build . . . . . . . Big-Boned . . . . . . . Delicate
Are you: . . Average Active . . Sedentary, out of shape . . Athlete, Bodybuilder
Did you exhale: . All the air you could . Normally . Attempt to have average air
How much intestinal gas do you think you have: . . Average . . Minimum . . A Lot
Your Weight: (lbs)
Your Height: (inches)
Baton/Float Letters You Used for Neutral Buoyancy:
Body Density: Your
Body Density: Your Bodyfat %:
Corrected Siri-2: Corrected Brozek: BMI Number:
Your Body Volume: liters, or cubic feet, including lung spaces.
The Measured Average Body Density here is that actually determined by the highly respected Hydrostatic Weighing procedure. This is the very accurate number that our system uses. The Adjusted Average Body Density is a mathematical adjustment made by all other systems to try to account for the air that remains in the lungs that cannot be expelled, which modified number they then use in their formulas. It makes for generally rather inaccurate and unrepeatable results, so our approach is far better.

The options regarding air in your lungs: There really is a tremendous advantage in trying to expel all the air you can, because once you have learned to achieve that level, it is pretty reliably constant. In our precise expectations of things, within two or three letters is realistic, which commonly means within around 1% precision and repeatability. In contrast, if you think you can just try to "always have the same amount of air in your lungs, whether at a standard exhale or some average amount of air, on our letters scale, you can easily show that you get results which are very different! If you try to do it at what you consider a standard exhale, you will likely be at about 45 letters above (heavier) than the maximum expelling mode which we use. In itself, that might not be terrible, but your repeatability of exhaling exactly the same is not good! The point is, one time you try it, it might be 35 letters heavier and the next time it might be 55 letters heavier, and your normal exhales might feel exactly the same to you. If your data can be off either way by five or ten letters each time, the bodyfat percentage data figures can vary by 7% to 10% each time, unexpectedly, the idea of trying to CHART the results becomes less possible! Your data might be varying by several percent up and down, just because of these differences. The value of learning to expel absolutely all the air you can is that once you get practiced at doing that, you are likely to have a rather consistent amount of air remaining in your lungs (very likely around 1.2 liters). Since that amount is pretty constant each time, your baton choices are more consistent and your results more accurate.

The highly respected and proven Hydrostatic Weighing (done in a swimming pool with a giant precise scale and hanging chair) REQUIRES the person to do maximum exhaling. In fact, even with that consistency of maximum exhalation, they STILL feel it necessary to REPEAT that exhaling and submersion TEN TIMES (over a period of about an hour) to then select and use only the three (highest) weight readings, because even then, they find variations in the amount of air a person exhales each time. The point here is that we are encouraging the same MAXIMUM EXHALING here, which is well proven to provide the most accurate data.

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The precision of our Baton/Float system is clear with these facts. For an adult man, a single letter difference is often only around 1/4 of 1%! It is not possible for anyone to consistently exhale all their air to that precision, but coming within a few letters is reasonably done, which means a Bodyfat Percentage value within around 1% or so, and that is very repeatably true. You are certainly free to TRY to exhale exactly the same normal amount but you will quickly see that you will sometimes rise and sometimes sink! These comments also make clear why we need to consider the far smaller amount of intestinal gas present, as it can affect the results by several letters. The carbon dioxide released by a can of carbonated pop in your stomach might require as much as six or eight letters higher Baton!

The main presentation page on a simplified Hydrostatic Weighing system is at: Bodyfat - Accurate and Easy Determination

Bodyfat - Combating Childhood Obesity Through Motivation (Childhood Obesity)

The Bodyfat - Simple and Accurate Measurement - PSA Storyline (storyline of the 30-second and one-minute PSA (Public Service Announcement) TV presentations.

The page that provides the PVC construction details for the Batons and Floats and all the printable Analysis Charts is at:
Bodyfat Analysis Weights - Filled PVC Plastic Batons ../public2/bodyfwp2.html

The page that provides the construction details for the Pepsi bottle-based Batons and Floats and all the printable Analysis Charts is at:
Bodyfat Analysis Weights - Pepsi Bottles and Pennies ../public2/bodyfwp3.html

The page that has the Bodyfat Percentage - Determining Accurate Bodyfat Easily which uses the Baton/Float letters and the dry body weight

This presentation was first placed on the Internet in December 2006.

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C Johnson, Theoretical Theoretical Physicist, Physics Degree from Univ of Chicago