Percent body fat is a tool used by many fitness professionals to evaluate your overall health status and disease risk. Personal trainers and dieticians use percent body fat as a tool to measure progress of their recommended exercise and diet regimens. The Jackson-Pollock formula is a validated method that uses skin-fold measurements to predict body fat.
Skin-Fold Measurements
Skin-fold measurements are one of the most accurate methods for gauging percent body fat. When compared to hydrostatic weighing, which the American College of Sports Medicine refers to as the gold standard in predicting body fat, skin-fold measurements fall within 3 percent. In addition to their accuracy, skin-fold measurements are also easy to administer and cost effective. The only equipment necessary is a set of quality skin-fold calipers and a trained technician.
Procedure
For the estimate of body fat to be accurate, technique is key. ACSM recommends that all measurements be taken on the right side of the body, while the subject is standing. The skin-fold should be grasped with the thumb and index finger and the calipers placed 1 cm away from the hold. The pinch should be held while the calipers rest for one to two seconds before being read. The technician should rotate through all the sites and then repeat. The American Council on Exercise recommends marking each site with a washable pen to ensure the same location is used during the repeat measurements.
Jackson-Pollock
There are dozens of formulas that can be used to predict percent body fat. The formula you use determines the number skin-fold sites you must measure. ACE and ACSM both say the Jackson-Pollock formulas are the most accurate. There are equations for both males and females and they have been generalized to include a wide population of subjects with regard to age and race. The three-site formulas are the most widely used for men and women according to the ACSM.
Male Sites
The sites used in the three-site formula for men are the chest, abdomen and thigh. The chest skin-fold is a diagonal fold just in front of the armpit and in line with the nipple. The abdominal fold is a vertical fold approximately 1inch to the right of the umbilicus and 1/2 inch below. And the thigh fold is another vertical fold, which is in the middle of the thigh, halfway between the hip crease and the top of the kneecap.
Female Sites
For women, the sites are the triceps, suprailiac and thigh. The triceps measurement is obtained by pinching a vertical fold on the back of the upper right arm, halfway between the elbow and the small bump on the back of the shoulder known as the acromion process. The suprailiac skin fold is a diagonal fold taken just above the ilium, or hip bone, in line with the armpit. And the thigh fold is taken on the front of the thigh, the same as in men, halfway between the hip and the top of the kneecap.
References
- "ACSM's Guidelines for Exercise Testing and Prescription," 8th edition. Lippincott, Williams & Wilkins; 2010
- ACE Fitness: Percent Body Fat -- Skinfold Method
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