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Assessment

Skinfold Body-Fat Assessment

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body-compositionskinfoldcalipersbody-fatjackson-pollockfield-method

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DefinitionA short reference note, not a full lesson.
Definition

Pinch subcutaneous fat at standardized sites with calipers and convert the sum (via a regression equation) to estimated body-fat percentage — the most common field method.

Detail

Skinfold measurement estimates percent body fat from the thickness of subcutaneous fat at standardized sites, assuming a predictable relationship between subcutaneous and total body fat. It is the most widely used field body-composition method. Full measurement technique lives in Skinfold (Fatfold) Measurement; accuracy/sources of error in Accuracy of Skinfolds (Five Assumptions).

Protocol summary: use calibrated calipers; grasp a fold ~1 cm from the marked site, measure ~1–2 s after releasing the caliper trigger; take 2–3 measurements per site (within ~1–2 mm) on the right side. Sum the sites and apply a population-specific equation:

  • Jackson-Pollock 3-site — men: chest, abdomen, thigh; women: triceps, suprailiac, thigh.
  • Jackson-Pollock 7-site — adds subscapular, midaxillary, and others. The summed skinfolds yield body density, converted to %fat (e.g., Siri equation: %fat = (495 / Db) − 450).

Accuracy: typically ±3.5% of the true value with a skilled tester and the right equation — better than BIA, not as good as DEXA/hydrostatic. Tester skill and site consistency are the dominant error sources; the same tester should perform re-tests.

Key facts

  • Estimates %body fat from summed standardized skinfolds via a regression equation.
  • Common equations: Jackson-Pollock 3-site and 7-site (site sets differ by sex).
  • Body density → %fat via Siri (%fat = 495/Db − 450) or Brozek.
  • Accuracy ~±3.5% with a skilled tester; tester/site consistency dominate error.
  • Right side, 2–3 reps/site; same tester for re-tests.

Connections

Sources

Cited in text — not yet linked
ACSM's Guidelines for Exercise Testing and Prescription (10th/11th ed.); Jackson & Pollock generalized equations (1978/1980); Siri (1961) body-density conversion.

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Atlas Connections

Bioelectrical Impedance Analysis (BIA)Closely related
Pass a tiny electrical current through the body and estimate body fat from how much it resists — convenient and fast, but very sensitive to hydration, food, and exercise.
Body Composition Assessment — Methods ComparedClosely related
No method is perfect; pick by needed accuracy, access, and cost — and once you choose one, re-test with the same method, because consistency beats absolute accuracy for tracking change.
DEXA (Dual-Energy X-ray Absorptiometry)Closely related
A low-dose X-ray scan that splits the body into fat, lean, and bone — and reports it region by region — making it a clinical/research reference standard for body composition.
Body Composition (Lean Body Mass vs. Fat Mass)
Total body weight divides into lean body mass (all non-fat tissue) and fat mass; some fat is essential for health.
Accuracy of Skinfolds (Five Assumptions)
Skinfold results can be inaccurate from tester error and poor site location, and they rest on five traditional assumptions that may not hold.
Skinfold (Fatfold) Measurement
Because roughly half of body fat lies just beneath the skin, measuring subcutaneous fatfolds lets you predict total body fat.