Skinfold assessment

A skinfold assessment uses calipers to measure a double layer of skin and subcutaneous fat at standard sites, then estimates body density and body fat percentage from the sum.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 221.},^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 278.} The NSCA’s strength and conditioning text describes it as the most valid and reliable body fat method accessible to most strength coaches, provided the tester is trained.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 278.}

Accuracy depends on the tester’s skill, caliper, client and equation; done well, estimates fall within about ±3.5% body fat for most clients.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 221.} The ratio of subcutaneous to total fat varies with age, sex and ethnicity, so the equation must fit the client, and a 3% to 4% error remains possible.^{3Hoffman, NSCA’s Guide to Program Design, p. 64.}

In practice

• Measure on the right side, on dry skin, before exercise.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 221.} Take at least two readings per site, plus a third if they differ by more than 2 mm or 10%.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 221.}
• Use the same caliper each time, and expect to practice on 50 to 100 clients before readings become consistent.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 221.}
• For tracking body composition changes, Helms suggests using the raw skinfold sum rather than converting it to body fat percentage.^{4Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 178.} Three equations applied to the same skinfolds produced group averages of about 10%, 15% and 20%, while a skilled tester’s sum repeats within about 5%.^{4Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 178.}