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A skinfold is a measure of subcutaneous body fat and skin obtained from several sites on the body using body fat calipers in order to determine body composition. A caliper, which is a hand-held instrument used by health professionals to measure fat stored under the skin, pinches a fold of skin and fat from each of these predetermined sites. The measurement in millimeters from each site pinched is then plugged into a formula to calculate the individual’s percent body fat. Over time, the skinfold test can be a reliable indicator of changes in body composition for individuals looking to lose weight and/or build muscle.
Developed in the 1970s as a simple and inexpensive way to analyze body fat, the skinfold test relies on an equation that factors the caliper measurements in millimeters with weight and age and produces an estimate of body fat percentage. Because the body fat caliper cannot measure visceral fat, or fat stored deep among the organs, it is not 100 percent accurate at gauging body composition. If utilized at regular intervals, however, it can measure changes in body fat over time with reasonable accuracy, provided that the same person performs the test each time. Another variable that can affect reliability of skinfold measurements is whether the individual administering the test pinches the exact same sites with a consistent amount of pressure, as human error can throw off the results.
Skinfolds can be taken from a number of different sites, depending on the formula being used. Most commonly, these measurements are obtained from three to seven locations on the body. When using the Jackson-Pollock formula, for example, skinfold measurements are taken at the triceps, the chest near the armpit, the side of the rib cage, the back at the bottom of the shoulder blade, the abdomen, the top of the hipbone, and the front of the thigh. At each site, the pinch should be taken vertically, horizontally, or diagonally. For instance, the pinch at the abdomen is to be measured vertically, with the fingers pinching inward on a vertical fold of skin and fat, whereas the pinch at the hipbone is to be measured diagonally.
The person administering the skinfold test is to begin by finding the specific site on each body part to be measured. On the triceps, that site is found on the back of the upper arm, midway between the shoulder and the elbow. The spot being measured should be in a relaxed and neutral position; in this case the arm should hang loosely by the side. Once the site is located, the tester should dig his thumb and first two fingers like a claw into the back of the arm, feeling for the muscle of the triceps.
Next, he should gather a vertical fold of skin and fat, firmly pinching the tissue while wiggling it slightly to separate it from the muscle beneath. With the calipers in his other hand and an overhand or inverted grip, he should pinch the gathered fold with the calipers just below the fingers on either side and note the measurement in millimeters. Each site should be measured twice, and an average should be recorded for accuracy. Once each site on the body is measured, the results can be plugged into an online calculator, found for free on a variety of websites to obtain an estimate of that person’s percent body fat.