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Infrared Reactance (IR)

Infrared reactance attempts to measure bodyfat thickness (and by extension estimate
overall bodyfat levels) by measuring the scatter of light through the tissue. Little research
supports its use or accuracy. IR is not recommended.

Skinfold calipers

Because the majority of bodyfat is under the skin, an individual’s total fat can be
estimated with skinfold measurements taken with calipers (spring loaded pinchers). Three or
more measurements are made at specific sites on the body which are entered into an equation
with weight, age and gender to estimate bodyfat. The estimation equations are accurate to
within plus or minus 5% (3) and tend to become less accurate at extremes of both leanness and
fatness. Although current research is questioning the overall accuracy of skinfold equations (3,4),
they are still considered the most accurate of the methods described above.

Due to the inherent inaccuracies involved in caliper estimations, it is suggested that
regular skinfold measurements be used to track relative changes rather then to provide absolute
measurements of bodyfat percentage (5). Table 3 compares the two skinfold measurements
below.

Table 3: Comparison of skinfold measurements

Skinfolds in millimeters

Date 1/1/98 2/1/98

Pectoral 5 4

Abdominal 15 12

Thigh 1 0 8

Total 30 24

We can see that this person has lost bodyfat, irrespective of the estimated bodyfat
percentages. Individuals using regular skinfold measurements should develop the habit of just
comparing measurements rather than relying on estimations of bodyfat.

With regards to bodybuilders (arguably the athletes most concerned with bodyfat levels), a
caliper measurement of 3-4 millimeters represents essentially zero subcutaneous fat. However
experienced bodybuilders know not to rely only on the numbers, but rather on appearance.
Striving for excessively low skinfold measurements may decrease muscle size, fullness and
symmetry. Ultimately, bodybuilders aren’t being judged on who has the lowest bodyfat level.
Rather they are judged by who looks the best on stage.