Site Selection

Site selection is very important and frequently a source of error in skinfold testing. The sites selected must match the particular protocol being used. There are two protocols usually involved, the 4-site system being the most commonly used.

This system is the same for male and female subjects and has been used as the basis for the correlations in this manual. The second system uses 3 sites, the sites differing for either male or female subjects, and are used in conjunction with the Body Density formulae (Jackson & Pollock).

The 4 Site System for Male and Female Subjects

1. Site 1 - Biceps
   The anterior surface of the biceps midway between the anterior fold and the antecubital fossa.
2. Site 2 - Triceps
   A Vertical fold on the posterior midline of the upper arm, over the triceps muscle, halfway between the acrosion process (bony process on top of the shoulder) and olecranon process (bony process on elbow). The elbow should be extended and the arm relaxed.
3. Site 3 - Subscapular
   The fold is taken on the diagonal line coming from the vertebral border to between 1 and 2cm from the inferior angle of the scapulae. (A diagonal fold about 1 to 2cm below the point of the shoulder blade and 1-2cm toward the arm).
4. Site 4 - Suprailiac
   A diagonal fold above the crest of the ilium at the spot where an imaginary line would come down from the anterior auxiliary line just above the hipbone and 2-3cm forward.

To calculate % Body Fat using LINEAR REGRESSION EQUATIONS of DURNIN & WORMERSLEY

BODY DENSITY = C[M(LOG 10 SUM OF ALL FOUR SKINFOLDS)]

THE SIRI EQUATION FAT% = [(4.95/BD) -4.5] x100 Alternatively use the look up tables

The 3 Site System for Male Subjects

1. Site 1 - Chest (Juxta-Nipples)
   A diagonal fold taken one half of the distance between the anterior auxiliary line and the nipple. (The anterior auxiliary line is the crease where the top of the arm, when hanging down, meets the chest).
2. Site 2 - Abdominal
   The vertical fold taken at the lateral distance of approximately 2cm from the umbilicus (2cm to the side of the umbilicus).
3. Site 3 - Thigh
   A vertical fold on the anterior aspect of the thigh, midway between the hip and knee joints (on the front of the thigh halfway between the hip joint, where the leg bends when the knee is lifted, and the middle of the knee cap). The leg should be straight and relaxed.

Using BODY DENSITY EQUATIONS (JACKSON & POLLOCK) to calculate % Body fat

MALE BD = 1.0990750 - 0.0008209 (X2) + 0.0000026 (X2)2 - 0.0002017 (X3) - 0.005675 (X4) + 0.018586 (X5)
Where
X2 = sum of the chest, abdomen and thigh skinfolds in mm
X3 = age in years
X4 = waist circumference in cm
X5 = forearm circumference in cm
Calculate the Male % Body Fat using THE SIRI EQUATION
FAT% = [(4.95/BD) -4.5] x100

The 3 Site System for Female Subjects

1. Site 1 - Triceps
   A Vertical fold on the posterior midline of the upper arm, over the triceps muscle, halfway between the acrosion process (bony process on top of the shoulder) and olecranon process (bony process on elbow). The elbow should be extended and the arm relaxed.
2. Site 2 - Suprailiac
   A diagonal fold above the crest of the ilium at the spot where an imaginary line would come down from the anterior auxiliary line just above the hipbone and 2-3cm forward.
3. Site 3 - Thigh
   A vertical fold on the anterior aspect of the thigh, midway between the hip and knee joints (on the front of the thigh halfway between the hip joint, where the leg bends when the knee is lifted, and the middle of the knee cap). The leg should be straight and relaxed.

Using BODY DENSITY EQUATIONS (JACKSON & POLLOCK) to calculate % Bodyfat

FEMALE BD = 1.1470292 - 0.0009376 (X3) + 0.0000030 (X3)2 - 0.0001156 (X4) - 0.0005839 (X5)
Where
X3 = sum of triceps, thigh and suprailliac skinfolds in mm
X4 = age in years
X5 = gluteal circumference in cm
Calculate the Female % Body Fat using THE SIRI EQUATION FAT% = [(4.95/BD) -4.5] x100