Hydrostatic body fat testing is the most accurate method of measuring the amount
of fat and lean (fat-free) mass a person has on his or her body. Just as a person
weighs a different amount on the Moon than on Earth, a person weighs differently
underwater than on land. Using measurements of a person's weight underwater and
weight on land, precisely how much fat a person carries can be calculated. If you've
heard of the "dunk tank" tests—that's hydrostatic weighing.
Back to index
Anyone who's serious about making progress towards their fitness goals needs accurate
information. For example, if you've lost 5 lbs, you may think that's great. But
how much of that was fat, and how much was muscle? Muscle helps burn fat, after
all. You can't rely on scale-weight only to know if you're making the progress you aim to achieve.
Getting a hydrostatic body fat test can answer this question. If you're trying to
lose body fat but maintain (or increase) muscle mass, you'll need detailed analysis
of your body composition changes. The better information you have, the better decisions
you can make to achieve your goals.
Back to index
The clinic has a large, shallow stainless-steel tank of water, which
you lie down in, just like if you were in a bathtub. After situating yourself, you'll expel out all the
air in your lungs and sink to rest on the scale on the bottom. This reading is your
wet weight. You'll do this a few times to get the most accurate measure. It's
easy and quick.
Once we have your wet weight, we use a scientific calculation based on
Archimedes' Principle along with your "dry" (scale) weight to determine your body composition and other data such as
your daily caloric expenditure. You'll receive a detailed print-out that explains your results
and tracks your history, if you ever chose to return to be retested.
Back to index
Only a few moments—until you've expelled all your air. Usually just five to 10 seconds. There's nothing to worry about!
Back to index
There is no other method in existence that is more—or as—accurate as hydrostatic
testing.
It's impossible to say that it's some-percentage (e.g. 99.9%) accurate, or what
the "margin of error" is. To say that, there would have to be a better method of
determining body fat that hydrostatic testing could be compared to. But there isn't.
The accuracy of other methods like caliper testing or BOD POD do have margins
of error—because their accuracies are a measure of how close their results are to
hydrostatic testing.
Back to index
To see how hydrostatic compares with other common methods, visit our page about hydrostatic weighing.
Back to index
Tests take approximately 10 to 15 minutes the first time. If you've been tested
before, it will take less time.
Back to index
We recommend wearing tight-fitting bathing suits or swim trunks under regular clothing.
Or you can bring your swimwear and change into it on board in the clinic's private
changing room.
Back to index
Your analysis will include a four-page report showing:
- Body fat and lean mass percentages and weights
- Where those figures places the subject on a scale of ideal health
- How much fat, if any, needs to be lost to reach composition goals
- Basal metabolic rate—how many calories/day are burnt without exercising
- Personal caloric intake and expenditure chart—how many calories/day are burnt based on the subject's various exercise activities
- Historical readings and progress, if more than one test has been taken
Back to index
We operate our mobile clinic at fitness clubs throughout Southern California. Specifically,
everywhere South of the I-10 freeway. For a current schedule of upcoming locations,
please visit our calendar. If you're outside of our
area, you can still get tested by another operator with the same state-of-the-art technology.
If you're interested in having our clinic appear at your club, refer a manager to our site!
Back to index
We try to return to each testing location every three to six months, although this isn't always possible.
Check our calendar for the location
you were last tested at or a different but nearby location. Be sure to tell your
club you're interested in being retested if you don't see them on the calendar!
Also, we'll shoot you an email to give you a notice a week before we next appear
at the location you were last tested at.
Back to index
Please do.
Back to index
The water in the tank is continuously filtered via a dual pump system
at all times while the clinic is in operation, chlorinated, completely replaced every day,
and approximately 92° F—better and warmer than pool water.
Back to index
Working out prior to testing will have no effect on the results. For consideration
of others though, we ask that you shower after working out and before being tested.
Back to index
Having a full stomach before being tested has a very minute effect on the
results. If you're concerned about getting the most accurate reading possible though,
it's a good idea not to have a large meal in the couple hours preceding your test.
Back to index
The mobile clinic has changing rooms for test subjects, and an entrace door that can
be closed during testing. Only one clinic technician is in the truck at any
given time. We do not share our results with anyone but you, nor any of your information.
Back to index