[quote]Waittz wrote:
[quote]Professor X wrote:
[quote]ryanbCXG wrote:
I will have to go look for it I use a diff email mostly now
My point was I don’t believe I am 8%. 10 if I am lucky. Showing calipers are in accurate even when you are lower bf but worse as you get fatter.
Though I am happy been at 220 for a month and waist has slowly been coming down. It’s a bit smaller than last summer when I was 205
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Calipers have about a 3% differential for error.
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Serious question, doesnt the variance increase/decrease with the person administring the test? [/quote]
This is from the book called methods of BF testing…
Skinfold Testing
The most common body fat test uses the skinfold caliper, a device that pinches your skin, pulling your fat away from your muscles and bones. You feel moderate discomfort, like when someone pinches your cheek. Typically the tester pinches three or four different sites on your body, such as your abdomen, arm, and back. The thickness of each pinch is plugged into a formula to determine your subcutaneous body fat level.
Many things can go wrong with a caliper test. The tester may not pinch exactly the right spot, or he may not pull all the fat away from the muscle. Or he may pinch too hard and accidentally yank some of your muscle. The calipers must exert a standard pressure and measure thickness to very small levels. Tests can vary greatly from tester to tester. Also, research shows that certain formulas are more accurate for certain ethnic groups, age ranges, and fitness levels.
Experts give this test a margin of error of four points, meaning your actual body fat percentage could be four points higher or lower than it actually is. Also tests show this test is accurate for about 90% of the population, when using the appropriate formulas. In laymen’s terms, if you are one of the lucky 9 out of 10, and your body fat measures 12% - it could really be anywhere from 8% to 16%. If you are the one in 10 (for example you are very lean or your body fat exceeds 30%) then all bets are off We have seem errors run as high as 10%.
Because of the consistency in results, the high percentage of people that this test is successful for, and the low margin of error, this is generally accepted as the best field test, outside of clinical testing such as hydrostatic, DEXA, and MRI.
For Optimal Results in Skinfold Measuring, the following protocol must be followed:
All technicians must participate at a workshop where they spend considerable time learning the exact sites and technique and then after practice all participants actually do an interclass correlation on a minimum of 15 subjects to determine their test-retest reliability at each of the seven sites. Jackson-Pollack sum of 4 equations. They are also taught that the caliper must be Lange or Harpenden. Jackson found .98 inter-tester correlations, indicating that if I’m good (reliable) and you’re good, then my measurement of an individual will be identical to yours. The workshops back this up by UWW. Depending on technique, obese individuals (>35%) can have skinfold tests done on them successfully. This assumes a two handed technique.
The problem lies in that very, very few technicians go to this extent to perfect their technique.