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Measuring Body Composition (Body Fat %)

Skin Fold Callipers VS. Bioelectrical Impedance!

Posted by Daniel_Meyer - February 17th, 2014

An organism’s composition reflects net lifetime accumulation of nutrients and other substrates acquired from the environment and retained by the body. A body composition analysis allows us to understand cellular functions and record metabolic changes within different populations.


Your body composition can also be important determinant of performance in many sports. For example, a high fat-free mass (FFM) is required for power and strength, whereas leanness (low body fat percentage) is important for sports in which body weight is unsupported or in which certain body aesthetics are considered necessary.


This article will compare and contrast two field assessments of body composition; bioelectrical impedance and skinfold thickness.


Methods


Skin Fold Callipers

Estimation of body fat percentage is created by measuring 3 to 9 anatomical sites on the body. Commonly, four skinfold sites are used; tricep, bicep, subscapular, and iliac crest. The procedure involves the tester pinching the skin at the appropriate site to raise a double layer of skin and the underlying adipose tissue, avoiding the muscle. The calliper is then applied 1cm below and perpendicular to the pinch and a reading in millimetres is taken two seconds later.5 Two measurements at each site are taken and the average of these numbers is calculated. Once the data is collected, it is input into a computer which calculates the sum of the skinfolds and equates the figures into a body fat percentage.

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Bioelectrical Impedance

Bioelectrical impedance works by passing a low electrical current through the body. The current passes easily through the fluids within the muscle tissue but is resisted as it passes through fat tissue. This resistance is known as bioelectrical impedance. The more accurate version of bioelectrical impedance uses the tetrapolar method of impedance using four electrodes placed on the hand and foot.


Throughout the test the person is required to lay supine with no contact between limbs.

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So Which Method Is Best?

A study I conducted at university showed that the bioelectrical impedance interprets body fat percentage lower than the skinfold method. This is contrary to the findings by Kitano1 who found that skinfold produced lower body fat percentage data in comparison to bioelectrical impedance but is in unanimity with the findings of Jackson.2


Skinfold anthropometry poses several disadvantages that may hinder the reliability of the data. Firstly, it is based upon the principle that a constant fraction of body fat is located subcutaneously. Previous reports on the equations used to calculate body fat percentage from skinfold measurements have also been shown to be population specific. Specificity has biological origins such as age, sex, ethnicity and technical origins and all have an effect on skinfold thickness. When skinfold is measured the pressure exerted by the callipers displaces some extracellular fluid. This displacement is marked when the extracellular fluid content of the subcutaneous adipose tissue is high leading to increased compressibility. This can have a negative impact on the accuracy of the data recorded.


The use of bioelectrical impedance within the athletic population has given rise to reliability problems associated with physiological factors and a limitation in prediction equations. Some of the physical considerations are the need to control conditions such as hydration, skin temperature, timing of last bout of exercise, glycogen stores and the chemical maturity in younger athletes. All these factors create conductivity issues that can affect the data recorded.


The validity and reliability issues surrounding both tests create some discussion on which test to use. In order to make this choice factors such as sample size, gender, ethnicity and practicality of the test must be considered.


Conclusion

The findings of the two body composition assessment methods have created no true clarity into which is the favourable option within various studies. Literature surrounding these methods also lacks continuity regarding which method is superior. In my personal opinion skin fold callipers can be more accurate, however, the person who does the test must be well qualified in taking the readings as this will make the overall body fat percentage more accurate.


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References:

  1. Kitano T, Kitano N, Inomoto T, et al. Evaluation of body composition using dual-energy X-ray absorptiometry, skinfold thickness and bioelectrical impedance analysis in Japanese female college students. Journal of Nutritional Science and Vitaminology. 2001;47(2):122-25
  2. Jackson AS, Pollock ML, Graves JE, et al. Reliability and validity of bioelectrical impedance in determining body composition. J App Phys. 1988;64(2):529-34
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MEMBER COMMENTS

WillWilkin

So I guess those cheap electronic scales aren't on the list.  I've read they are not accurate in their 5 but they can be useful in tracking the direction of change in your composition.

Scott_Herman

Well, as long as you adjust for the 2 - 3% plus or minus, you can still track with the digital scale :-D

Brolle81

How accurate are those Dexa scans? Not that I know if there anyplace here in my country where I actually could perform one and not to mention how expensive that might be. But that Calipers are slighty off due to many factors I knew just as well as impedance. Calipers worst enemy I suppose is the person holding it. The one who performed it on me stated first measure that I was 18% and then I had full visible 6 pack abs and biceps veins visible which doesn´t add up with that percentage in my world. Second time he measuered me he stated I was 15% but a lot of people that I asked which trains a lot stated I was more like 12-13 %. He did a 4 point reading biceps , triceps abdominal and lower back reading with a harpender caliper. 

Scott_Herman

There will always be 2 - 3% chance of it being off  a bit, but calipers are fine to use!

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