Skinfolds

Question 1

Why measure body comp.?

Answer 1

• Quantification of the structural components of the
body (muscle, bone and fat) is useful for:

– Medical purposes, e.g. assessing the impact of
• Weight-loss programmes
• Exercise interventions

– Enhancing performance, e.g. to monitor
• Fat loss
• Muscle gain

Question 2

Methods to determine body

composition?

Answer 2

• Hydrostatic weighing
• Dual energy x-ray absorptiometry
• Air displacement plethysmography
• Bio-electrical Impedance Analysis (BIA)
• Skinfold measurements

Question 3

Why do we measure skinfold:

Rationale?

Answer 3

• A ‘skinfold’ is the thickness of a compressed double fold of skin, including subcutaneous fat

• The amount of fat in the skinfold is related
to % body fat

• Therefore, skinfold thickness can be used
to determine % body fat

• Skinfold measurement is also an essential part of determining somatotype (later session)

Question 4

Where and how do we measure skinfolds?

Answer 4

• Skinfold measurement sites:
– Are standardised (follow written instructions)
– Must be accurately located and marked
– We will use 8 measurement sites (see later)

• Site inaccuracies can cause substantial errors in estimates of % body fat

• Skinfolds are measured using high-quality
Harpenden callipers

Question 5

Detailed Example:

Subscapular skinfold?

Answer 5

• Subject stands with arms by sides
• Right arm behind back can help
• Site marked at inferior angle of scapula
• Left index finger placed on the mark
• Thumb placed inferior to this point
• Lift a diagonal (45o) fold, infero-laterally
• Caliper is applied 1 cm lateral to the finger and thumb

Question 6

Practical hints on the skinfold

measurement technique 1

Answer 6

• Thumb and index finger should be placed
a few cm on either side of the measurement site

• Bring finger and thumb together to pinch the skin and underlying fat between your finger and thumb
• The pinch should have parallel sides

• Hold the pinch perpendicular to the body
surface

• Apply the calliper jaws half way down the skinfold

Question 7

Practical hints on the skinfold

measurement technique 2

Answer 7

• Hold the skinfold firmly throughout the measurement

• i.e. Don’t release the skinfold even when the calliper has been
applied

• A reading is taken 2 seconds after releasing the calliper

Question 8

Example: Estimating body

density and % body fat?

Answer 8

• The equations of Jackson et al. (1980) are suitable for the general adult population (separate male and female equations):

e.g. for Men:
D = 1.10938 –0.0008267x + 0.0000016x2 –0.0002574y

– y = age in years (e.g. 20 years)
– x = sum of triceps, thigh and suprailiac skinfolds (e.g. 55 mm)
So: D = 1.10938 –0.0008267 x (55) + 0.0000016 x (55)2 - 0.0002574 x (20)
= 1.063604

• The Siri equation gives % body fat:
– % fat = (495 / D) –450 = (495 / 1.063604) –450 = 15.4%

Estimated accuracy of skinfolds to predict % body fat is +/-3.5%