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February 15, 2010 | Exam Preparation Blog

The Weighty Subject of Body Composition

***8/26/14: Please refer to Physiological Assessments: Anthropometric Measurements for more up-to-date information on this topic.

Body Composition

Body composition testing and evaluation is a popular subject among exercising individuals. Everyone wants to know how fat or lean they are and how soon they can lose the weight. As an exam candidate, you are presented with a wide variety of options – underwater weighing, circumference measurements, and body mass index to name a few. So which one is best? Which one should you focus most on studying? Which one will you end up using?

Body composition can be defined as the makeup of the body in terms of the relative percentage of fat-free mass and body fat. Our ways for testing body composition include hydrostatic weighing (underwater weighing), bioelectrical impedance, body mass index, and anthropometric assessments - circumference measurements, waist to hip ratio, skinfold measurements, and girth measurements.

Of these measures, hydrostatic weighing is considered the ‘gold standard’ of body composition assessment. However, hydrostatic weighing is a complex process that requires expensive equipment, time, and dedication on the part of the person being assessed (it’s not easy blowing all the air out of your lungs while you are submerged!). Bioelectrical impedance is a method many trainers are familiar with – think of the small hand held devices, which the client holds with both hands as a small current passes through their body. Bioelectrical impedance can be a quick and easy method for assessing body composition, but the accuracy of this method goes downhill considerably if the client does not follow specific guidelines required for best results.

Body mass index should be familiar to most everyone as it has been around, and been used, for quite a while. Yes, this is a formula you should know and be ready to calculate (hint, hint). But when we are only using height and weight to determine someone’s body composition we run into the obvious challenge of no distinction between fat weight and lean weight. Muscular individuals may measure as obese, when in reality they have a very low percent body fat. Although BMI has its place, it shouldn’t be considered the first choice for accurate understanding of all aspects of body composition.

Anthropometric body composition assessments may be considered the easiest and least expensive ways of measuring body composition. Circumference measurements can be used as a way of estimating body fat, utilizing the body density formula (which we’ll discuss in a little more detail next week!). The ACE 4th edition Personal Trainer manual talks about both circumference measurements and girth measurements. These two assessments use different anatomical landmarks, but are essential measuring the same thing. Circumference measurements can also be used to determine waist to hip ratio. Although waist to hip ratio only looks at one segment of the body, it is vital because upper-body or abdominal obesity is known to increase health risk.

The final method of body composition assessment would be skinfold measurement. This is one that most personal trainers should be familiar with. Skinfold measurements can be easily done in a field setting and if the measurements are done correctly, the results can be valid and almost as reliable as underwater weighing. However, accurate site selection and proper ‘grasp’ of the skinfold are key to a valid measurement.

So with all these options for measuring someone’s body composition, which is the right one to use – in practice or during your exam? As usual, that depends on who the client is and what their goals are. Would skinfold measurements be the most accurate assessment tool with an obese client? Why not? Is Body Mass Index the best tool for large group assessment of body composition? Would a bioelectrical impedance device be the correct choice when working at a public health fair, when you didn’t have a chance to convey testing standards to the client ahead of time?  Who might benefit most from waist: hip ratio? How can circumference measurements be used as a motivational tool when working with a client who is new to exercise or has a significant amount of weight to lose?

As you review your materials and prepare for your exam, keep these types of questions in mind. Not only for utilizing body composition assessments, but for other physical fitness tests.

Questions? Contact an Education Consultant at 1-888-825-3636 x782.

By April Merritt
April Merritt holds a bachelor’s degree in Exercise Science, a master’s degree in Health Promotion, and several ACE certifications including Personal Trainer, Group Fitness Instructor and Health Coach.

April Merritt holds a bachelor’s degree in Exercise Science, a master’s degree in Health Promotion, and several ACE certifications including Personal Trainer and Health Coach.