Simple and Accurate Bodyfat Measurement

A set of Public Service Announcements (PSAs) are being completed which should air on many television stations, which show how this method works. The following discussion follows the storyline of those PSAs.

Here are also some streaming video files of the PSAs:

• 30-second PSA, low bandwidth
• 30-second PSA, med bandwidth
• 60-second PSA, low bandwidth
• 60-second PSA, med bandwidth

• This method is so much fun that children will often be reminding their parents about the day they get to again have their bodyfat tested. As is convenient to the parents, they then go to a nearby YMCA, or a local Health Club or a local Public High School or Park Department swimming pool. No knowledge of swimming is necessary!

  We believe that around 74,000 such facilities should be available (in the US), providing this testing either as a totally FREE service to their community or possibly for a $1 charge. There are approximately 30,000 public high schools and another 6,000 private high schools, 7,000 post-secondary schools, 17,000 membership-based health clubs, thousands of municipal swimming pools, and other assorted public pools which might be used for this purpose. Since a swimming pool can continue to be used for other swimmers, there is no disadvantage to the owner of the pool. Since this procedure is only done in the shallow end of the pool, and it is so simple that no Staff people need to be involved, there are not even any complications to the normal operation of the facility. For membership-based health clubs, publicizing the offering of this free service to the local community should get many new prospective Members in the doors! So we believe that the majority of those 74,000 facilities should have strong incentive to provide this service. One should be near you!

  For any of these facilities, there is not even any significant cost involved! For a High School, less than $50 of materials (from a local home supply store) would provide a Shop Class a very interesting project, since this web-site provides for free all the directions needed to assemble the needed Batons. Health Clubs could have their Maintenance Personnel make them. The point is that for as little as $50 total expense, any of these 74,000 facilities could offer this wonderful service to their local community.

  

• Once the family arrives at the Health Club or High School, the adult "signs in" and the kids each get an identifying card or the equivalent.

• Once at the swimming pool, the family checks in with the Lifeguard. When the Lifeguard sees the identifying cards, he immediately knows that they are going to use the Bodyfat Analysis Batons. If this is a family that the Lifeguard does not recognize, he asks if they need any directions. He can also check to see if the kids can swim, and might remind them that they must stay at the shallow end of the pool.

  The Lifeguard will not have any special responsibilities for this family's activities. He/she will be able to watch the entire pool, as normal. As far as the Lifeguard is concerned, these kids are no different than anyone else in the pool.

  

• When one kid is in the pool, a second person must be up on the pool deck. This person gets different Batons from the storage rack as necessary (while leaving most of them there in the rack so other families could also be using them at the same time). NO RUNNING! The person up on the pool deck also needs to observe whether the child is floating or sinking. This just means whether you see any part of their back above the water! This second person could be the parent or it could be a brother or sister or a friend.

• Near the pool, there is a set of the Bodyfat Batons, of all different sizes and precise weights, each identified by a letter of the alphabet. This is the location from where the necessary Baton will be obtained (and later returned, such that other families can use them!). Nearly all of the Batons will sink in the swimming pool if they are released, so you should not let go of any of the Batons while you are in the pool. However, if and when that happens, it is easy for someone to pick them up off the shallow-end bottom of the pool. They are all plastic coated, so they would not chip the pool bottom or pool deck if dropped. Some of them are fairly heavy, so they are NOT to be thrown, and the Lifeguard would be right to order anyone away from the pool if one was ever thrown!

  The Batons A through X are in order as to their weight. Behind them, you can see the two much larger (and heavier) Y and Z Batons which are only needed for people who either have an extremely high bodyfat percentage or they weigh far more than any kid probably should! (They are primarily intended for some adults.)

  Near the back of the rack, you can also see the two Float Batons, which only need to be used for kids or adults who naturally sink in a pool.

  The storage rack we have used has a specific place for each of the Batons, with matching letters that show where they belong. However, a different sort of storage rack could be used, even just lining them up on a shelf or the pool deck. The rack shown has the advantage of having a letter on the rack right under each Baton, so it is obvious to where it is to be returned.

  The storage rack is not right at the pool, but in a location where people would not stumble over it.

  

• When a new child is to first try this system, it is helpful if an experienced child shows how to hold the Baton against the belly and then curl up in a ball.

  When the child in the pool does this, he/she starts out simply standing. Once the feet are lifted up off the bottom of the pool (to curl up into that ball), the child either floats or sinks, and part of the back is either visible or not visible above the water. Simple! The idea of this "game" is to find the LOWEST LETTER BATON (or largest Float) that will stop you from floating with your back above the water. So the person in the pool can try holding ANY of the lettered Batons to see if you float or sink, or no Baton at all, or even one of the Float Batons, usually with one of the lettered Batons, too.

  Once the feet are lifted up off the bottom, only three things are possible!

  (1) The child could float. In this case, she is holding the '&' Float and the 'E' lettered Baton, and a portion of her back is visible above the water (this indicates that the average density of the child plus Baton is slightly less than that of the water of the pool). She would either need to try to blow out (exhale) more air from her lungs or use a heavier (higher letter) Baton and try it again. Since each try only takes a few seconds, it's "no big thing!" Since this is a "competitive game" to kids, they may want to try several times to blow more and more air out of their lungs, to be able to use the lowest letter Baton!

  (2) The child could sink, clearly going down toward the bottom. This indicates that a lower letter Baton could be tried, in other words "winning"!

  At any time the child could simply let go of the Baton if there was any fear, to immediately bob up to the surface. And just putting the feet down works too, to get the head above the water!

  (3) Or the child could sort of "hover", in this case while holding the '&' Float and the 'F' lettered Baton, without really floating or sinking very fast. This last situation is the goal. With this situation, the combination of the child and the Baton(s) have EXACTLY the same "average density" as the water in the pool. That water's density is precisely known to be 0.9978 gm/cc (not actually 1.0000 gm/cc because the water is warmer than 39°F). The Batons are all precisely designed, so there is certainly ONE of the Batons that will permit this hovering (or very slow sinking)!

  From the kid's point of view, it represents the SMALLEST LETTER Baton (or largest float) where she is not clearly floating.

  It is NECESSARY to exhale all the air possible from the lungs in order to get really accurate results. If a child does not exhale much air, that air in the lungs acts as an extra "float" and then ALWAYS makes it necessary to use a higher letter Baton to stop floating! Exhaling more means a BETTER SCORE! In the first several weeks of doing this, nearly all children's Progress Charts will seem to show impressive improvements in Bodyfat Percentage, but it is probably misleading! As a (competitive) child wants to "get a better score" than last week, he/she tends to learn to force more air out of their lungs. That way they get a "better score"! So it is commonly several weeks (of competitive practice!) before a child is exhaling ALL the air they can, and in the meantime, their Progress looks very impressive! Once they are exhaling all that air (there is ALWAYS some air that remains in the lungs, but it is a pretty constant amount and does not affect this process), the precision of this system starts to really show. Since each week's results is generally accurate to better than 1%, the Progress Chart shows any "trends" toward better or worse bodyfat percentage. This does NOT mean that any specific week might be off that line (usually higher) because the child might not exhale as much air that week, or he/she might have just drunk a carbonated soda or recently eaten something that makes intenstinal gas. The point is, the TREND of the line on the Progress Chart is extremely reliable.

  

• At that point, the testing is done! The kid only HAS to get out of the pool if the parent insists, or to be the on-deck assistant so that her sister (in this case) could do the same testing.

  The child's dry body weight (on a standard scale) (in this case around 80 pounds) and the letter of the Float and Baton (in this case '& + F') are then looked up on an Analysis Chart. No complicated calculating ever needs to be done (because it was already done earlier for you!) The Analysis Chart is set up like a simple multiplication table, and the Bodyfat Percentage is simply the number in the box where the Weight (80) and Baton Letter (F) cross. There are a whole series of Analysis Charts, which have pre-calculated figures for every possible person between 30 lbs and 400 lbs, and they are provided (as DOC files) in this web-site (from the main Bodyfat web-page linked below here). Any computer could simply print out a copy. We recommend that it then be laminated to keep it from getting wet!

  

• The PSAs end with the still-competitive children discussing their results. They would each have a "competitive awareness" regarding their diet and exercise! They may even ASK their parents for "healthier foods". Even more amazing, when they are AWAY from their parents, they may CHOOSE to pass on french fries or junk foods! Kids just normally do not have the self-control to make such decisions, but this (fun) activity is competitive enough to possibly encourage them to sometimes show such restraint!

  

• At the family dinner table, the kids might even express (mild) criticism when fed "convenient" meals by a working parent. So it might even be a reminder to the parents to consider providing healthier foods for their families!

• Similarly, a kid watching television or playing their GameBoy might suddenly decide to go outside and do "active" things, to exercise to get better results next week on their Baton!

Credits, regarding the PSAs

Concept developed, and script written by: Carl Johnson

Public Service Announcement (PSA) created by:
Governors State University Media Department, headed by Prof. Dan Nearing

Have a "normal" amount of air in your lungs, NOT having severely exhaled or inhaled. And then simply float stationary! Your friend sees (or maybe even measures) how much of your head sticks out of the water! If you do NOT float and sink toward the bottom, your bodyfat is likely to be around 13% or lower. If your friend sees TWO INCHES of the top of your head above the water, you are likely to be around 24%. If your friend sees about FOUR INCHES (essentially to the very top of the earlobes), you are likely to be around 40%. If around SIX INCHES (essentially to the earholes, and your eyes are above the water) then you are likely to be around 57%. You might see from the large changes in bodyfat numbers due to rather small differences in the amount of the head being visible, that this method is only very approximate, with plus-minus 10% being expected. It only provides a ball-park number!

We mention this because there are a LOT of people who have been told that they have 8% or 4% or 11% bodyfat, due to using the extremely inaccurate bodyfat caliper method or electrical impedance (methods absolutely proven to regularly be 15% off either way, so in other words, meaningless except for bragging purposes.) A person could try to alter this method by intentionally normally exhaling first, which makes you float around one inch lower, which would appear to give an estimate of around 6% lower. By attempting to exhale all the air you can, you can lower your body by about 3 inches, which can give the appearance of around 16% lower estimate. The point is that by simply altering the amount of air in your lungs, you could change this reading by as much as 16%, another indication of why the far more accurate and repeatable Batons and Floats is desirable. If you really want to believe that you are at 8% or 11% so you can brag to your friends, there are many ways you can create such a number. However, if you actually want a REAL number for bodyfat, this very crude method can get you within about plus-minus 10%, and the Batons-Floats can get you within about 1%.

Bodyfat Analysis (specifically directed at Childhood Obesity)

The 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:
http://mb-soft.com/public2/bodyfwp2.html

The page that has the Bodyfat Calculator which uses the Baton/Float letters and the dry body weight

This presentation was first placed on the Internet in March 2005.

Other Health Related Web-Pages in this Domain

( http://mb-soft.com/public/index.html )

C Johnson, Physicist, Physics Degree from Univ of Chicago