Taking Skinfold Measurements

Skinfold testing, also known as calliper testing is a commonly used method to determine a clients body fat percentage.

This technique of measurement is based on the densitometry technique (underwater weighing) and the prediction equations are ‘population specific’.  That means originally to come up with the equations to calculate body fat from calliper measurements a whole lot of people were underwater weighed and then calliper tested.  Their results from the underwater weighing were used to work out what equation was needed to convert their calliper measurements to a body fat percentage.

The equations actually only predict body fat within 3-5% of the value obtained from underwater weighing and only if the person is similar in age, gender, state of training, fatness and culture to the population from which the equations were originally derived. 

In other words, there is the real possibility that calliper measurements will be inaccurate, misleading and unreliable in many instances.  That means personal trainers expose themselves and their clients to significant risks.  If a client trains well for six weeks then finds out their body fat percentage hasn’t changed (or worse has become larger) because there were errors in the equations used, or the measurements taken, or the consistency of the measurements, the result will be one of disappointment, frustration and de-motivation. 

This is why we recommend extreme caution and very strict use of protocols if you are going to use calliper testing in any way.  If you do, it is best just to use a ‘sum of skinfolds’ where you add up all the measures you take and don’t convert to body fat percentage as this, at the very least, removes the errors in equations and comparisons to sample populations which can throw your figures off.

As this technique is commonly used in the fitness industry and some clients may even specifically request it, it is important that you understand the protocol and are competent at completing it.  Remember though, choose wisely the circumstances in which you use this type of measurement and pick the test that best suits your client goals and will provide valid, reliable and positive results.

If you are going to use callipers as a form of measurement it is recommended you practice your skill in measuring skinfolds on between 50-100 ‘practice’ participants to develop your proficiency. 

Procedures for skinfold measurement:

You need to firmly grasp a fold of your client’s skin between your thumb and index finger and lift this up.  The skinfold should include two thicknesses; one of skin and one of the subcutaneous fat, but no muscle or fascia. 

Place the contact surface of the callipers at a 90 degree angle to the skinfold approximately 1cm below the fingers.  Slightly release the pressure between the fingers, but remain holding the skinfold so that a greater pressure is applied by the callipers.  Release the handle of the callipers and read the needle to the nearest 0.1mm approximately 4 seconds after the pressure is released.

Here are some key points to remember when taking skinfold measurements:

• Ensure you are careful in locating the anatomical landmarks used to identify the skinfold site
• Take all skinfolds on the right side of the body (for reliability)
• Ensure that you take the skinfold in a rotational order (circuit) and do not complete consecutive readings at each skinfold site
• Grasp the skinfold firmly between your thumb and index finger of your left hand.  The skinfold is lifted 1 cm and recorded with the callipers held in the right hand
• Keep the fold elevated while the measurement is recorded
• Take the skinfold measurement 4 seconds after the calliper pressure is released
• Take a minimum of two measurements at each site.  The acceptable range between repeated measures is 1mm.  If the values vary by more than 1mm take an additional measurement and use the average of the three measurements
• Skinfold measurements should not be taken when the skin is wet or after exercise
• Remember age, size and state of hydration may affect skinfold measurement

The ‘Durnin and Womersley’ four-site skinfold test

The most commonly used skinfold test is the Durnin & Womersley four site test, devised in 1974 (yip – it’s pretty dated!).  This test uses the sum of the triceps, biceps, subscapula and suprailiac skinfolds to produce an estimate of body fat for males and females.

The following images and instructions will help you to locate the four sites used in the Durnin and Womersley test.  Once you have successfully located the sites use the previous instructions on how to take a skinfold to complete the four site test.

Once you have completed and recorded the measurements of the four sites, refer to the following tables for the conversion of the sum of the four skinfolds to % body fat and for a rating of the sum of the four skinfolds for males and females of normal and athletic ability.

Tricep Skinfold

• Vertical fold
• Located on the posterior midline of the upper arm
• Measure halfway between the acromion (bony point of the shoulder) and olecranon processes (bony point of the elbow)
• Arm held freely to the side of the body

Biceps Skinfold

• Vertical fold
• Located on the anterior midline of the upper arm over the belly of the biceps muscle
• Located 1 cm higher than the level used to mark the triceps site

Subscapula Skinfold

• Diagonal fold
• Located 1 to 2 cm below the inferior angle of the scapula (the bottom of the shoulder blade)
• If you struggle to locate the bottom of the shoulder blade then ask your client to raise their arm up behind their back – this should make the scapula become more prominent.

Suprailiac Skinfold

• Diagonal fold
• Located 1 cm above the anterior superior iliac crest (top of the hip bone)
• Locating this landmark may require you to ‘poke’ firmly through thick subcutaneous layers of fat to find the bone underneath.

Once you have recorded the skinfolds at each site you could simply use these measurements to compare with subsequent measurements to show change in the clients skinfold over time (which we recommend), alternatively you can add the sum of the four sites together to work out an estimate of your clients body fat percentage using the following table.

Body Fat % Conversion Table