Course:KIN366/ConceptLibrary/Body Composition

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Movement Experiences for Children
KIN 366
Instructor: Dr. Shannon S.D. Bredin
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Important Course Pages
Lecture Notes
Course Discussion

Body composition is used to describe the percentage of fat mass (FM) and fat-free mass (FFM) or lean body mass (LBM). Its origin started back in 400BC were just elements of the body were looked at to now where there are various methods to classify one’s body composition. Body composition has become a major concern in today’s society due to the prevalence if childhood overweight and obesity increasing. With various methods to measure children’s’ body composition practitioners have many options to chose from; skinfolds, circumferences, skeletal diameter, body mass index, dual-energy X-Ray absorptiometry, and bioelectrical impedance analysis.


The study of body composition starts back to 400BC where the Greeks identified the basic elements of the body as hot, cold, moist, and dry. It was not until the 19th and 20th century when Justus van Leibig and J. Matiegka started working with muscle mass and anthropometry. In 1871 body mass index (BMI) [a method to classify individuals based on height and weight] was first introduced. In 1942 Behnke and colleges developed the first the underwater weighing technique based on a two-component model of fat mass (FM) [all extractable lipids from adipose and other tissues in the body] and fat free mass (FFM) [all residual lipid-free chemicals and tissues including water muscle, bone, connective tissue, and internal organs], which was further developed, by Brozek and Keys through densitometry. In 1984 Brussels and colleges conducted the first cadaver study looking at every tissue and weighing them all and accounting for various tissue levels.

Obesity Epidemic

Over the last two decades, the prevalence if childhood overweight and obesity has increased. The prevalence of obesity (10.9%) has doubled and prevalence of overweight (15.5%) has increased for children in Canada (Styne, 2001). This becomes a major concern cause those children whom are overweight or obese, as children tend to become overweight and obese adults whom have relatively high risk of developing diseases and disorders associated with excess body weight. Because of these health implications, the epidemic increase in childhood overweight and obesity has stimulated mush interest in identifying accurate ways to assess the body composition of children in school and clinical settings.


Body composition is used to describe the percentage of FM and FFM or lean body mass (LBM) [fat-free mass plus essential lipids]. There are various models from which one can look at body composition. Each model is broken up into different components of the human body and composition of it. Some models works better for certain groups within the population. Not every model works for everyone.


The earliest two-component model was pioneered by Behnke et al in 1942, was based off of measuring body density (Db) [total body mass expressed relative to total body weight]. Behnke et al. established an inverse relationship between Db and adiposity and concluded that excess fat is the main factor affecting Db. Later (1953), Behnke developed a concept consisting of FM and LBM. This concept assumed that the density of the LBM was constant for everyone. At the same time Keys and Brozek (1953) developed a two-component model equation to estimate percent body fat (%BF) from Db. In 1963 the Brozek et al. equation was formed. %BF = (4.57/Db – 4.142) x 100, this equation has been widely used over the years.

The following assumptions are made to estimate percent body fat (%BF) [fat mass expressed as a percentage of total body weight] from Db using the two-component equation.

  1. The densities of the fat and FFB components (water, mineral, and protein) are additive and are the same for everyone
  2. The proportions of water, mineral, and protein in the FFB are constant within and between individuals
  3. The individual being measured differs form the reference body only in the amount of body fat (triglyceride) or adipose tissue


In 1961 the first three-component model equation was created by Siri and colleges. This new equation adjusts for Db to the relative proportion of water in the body. This model divides the body into three components; fat, water, and solids and assumes a constant density for the protein-to-mineral ratio. Similar to Siri’s 1961 equation, Lohman (1986) devised a three-component equation that accounts for variability in the relative mineral content of the FFM and divides the body into fat, mineral, and protein + water fractions.


The four-component model divides the body into fat, mineral, water, and protein components, thereby eliminating the need to make assumptions about the relative proportions or these components in the body when compared to the other models (two-component and three-component). A four-component model is generally used to estimate %BF from Db in cases in which both the hydration and the relative mineral content of an individual varies greatly.


The six-component equation by Wang et al. 1998, divides the body into six components water, nitrogen, calcium, potassium, sodium, and chloride. This equation requires the direct analysis of the chemical components of the body.

Methods of Measurement

There are various methods used to measure and calculate one’s body composition; each method their own advantages and disadvantages. Specifically this page will focus on the methods that work for children when measuring their body composition.


In the early 1900s, the thickness if subcutaneous adipose tissue was measured for the first time using the method termed by Brozek & Keys (1951) as skinfold (SKF) measurement. With the nature of SKF measurements to be easy to administer at a relatively low cost it has been widely used in field and clinical setting to estimate total body fatness. Skinfolds are an indirect measure of the thickness of subcutaneous adipose tissue. When using the method to estimate total Db to derive %BF values, certain basic relationships are assumed: the SKF is a good measure of subcutaneous fat (Hayes et al., 1988), the distribution of fat subcutaneously and internally is similar for all individuals within each gender and age (Jackson, 1984; Lohman, 1981), because there is a relationship between subcutaneous fat and total body fat the sum of several SKFs can be used to estimate total body fat (Jackson & Pollock, 1976), and there is a relationship between the sum of SKFs and Db (Jackson, 1984).

It takes a great deal of time and practices to develop skill as a SKF technician. For obtaining the best results one must adhere to the following standardized procedures. (Harrison et al., 1988)

  1. Take all SKF measurements on the right side of the body.
  2. Carefully identify, measure, and mark the SKF site, especially if you are a novice SKF technician.
  3. Grasp the SKF firmly between the thumb and index finger of your left hand at a distance of 1cm above the marked site and then life the fold. This will allow you to place the caliper jaws directly on the marked site.
  4. Lift the fold by placing the thumb and index finger 8cm apart on a line that is perpendicular to the long axis of the SKF. The long axis is parallel to the natural cleavage lines of the skin. For individuals with extremely large SKFs, you will need to separate the thumb and finger more than 8cm to life the fold.
  5. Continue grasping the fold with the left hand after the caliper jaws have been placed in it and keep the fold elevated while the measurement is taken.
  6. Place the jaws of the caliper perpendicular to the fold approx 1cm bellows the thumb and index finger and halfway between the crest and the base of the fold. Release the jaw pressure slowly.
  7. Take the SKF measurement 4sec after the pressure is released.
  8. Open the jaws of the caliper to remove if from the site. Close the jaws slowly to prevent damage or loss of calibration.

In addition to improving one’s technical skills, it is important to develop one’s interpersonal skills when administering SKF. To develop interpersonal skills, one expert offers the following suggestions: (Habash, 2002).

  1. Prior to the scheduled test session, instruct clients to wear loose-fitting clothes that will allow east access to the sites to be measured.
  2. Often clients are apprehensive about having their SKFs measured, particularly when they are meeting you for the first time. During the testing, you should put your client at ease by establishing good rapport; projecting a sense of relaxed confidence; and creating a test environment that is friendly, private, safe, and comfortable.
  3. The private room should be uncluttered and should have a small table for calipers, pens, clipboards and a chair for clients who are unstable standing or may need to rest during the testing.
  4. Some clients will feel more comfortable having their SKFs measured by a technician of the same gender. If this is not feasible, you can ask your clients if they would like another person of the same gender to observe the test.
  5. Educate your clients about the SKF tests by talking about the purpose and use of the measurements, pointing to the SKF sites to be measured on your own body, and demonstrating on yourself how the SKF is measured.
  6. Limit your verbal and facial reactions to the data being collected during the test.

The accuracy and precision of SKF measurements and the SKF methods are affected by the technician’s skill, the type of SKF caliper, client factors, and the prediction equation used to estimate body fatness. (Lohman et al., 1984). The errors that are affected by the technician skill that occur are; there is a difference of 3-9% between SKF measurements between technicians (Morrow et al., 1986), the anatomical descriptions for specific SKF sites are not all the same for all SKF equations (Behnke et al., 1942), and there is no exact number of measurements that one needs to take at each SKF site (Jackson & Pollock, 1976). The errors that are affected by the client are; their hydration level (Ward et al., 1999) and the state of the client’s muscle or fat mass (Gray et al., 1990).

Circumference and Skeletal Diameter

A circumference is a measure of the girth of body segment (eg. arm, thigh, wrist, and hip). A skeletal diameter is measure of the bony width or breadth (eg. knee, ankle, and wrist). Practice is necessary to become proficient in measuring skeletal diameters and circumferences. The following are standardized procedures that will increase the accuracy and reliability of your measurements: (Callaway et al., 1988; Wilmore et al., 1998).

  1. Take all circumferences and bony diameter measurements of the limbs on the right side of the body.
  2. Carefully identify and measure the anthropometric site. Be meticulous about locating anatomical landmarks used to identify the measurement site.
  3. Take a minimum of tree measurements at each site in rotational order.
  4. Hold the skeletal anthropometer or caliper in both hands so the tips of the index fingers are adjacent to the tips of the caliper.
  5. Place the caliper on the bony landmarks and apply firm pressure to compress the underlying muscle, fat, and skin. Apply pressure to a point where the measurement no longer continues to decrease.
  6. Use an anthropometric tape to measure circumferences. The zero end of the tape is held in your left hand, positioned below the other part of the tape help in your right hand.
  7. Apply tension to the tape so that it fits snugly around the body part but does not indent the skin or compresses the subcutaneous tissue. To apply the appropriate tension and to increase the reliability of your girth measurement.
  8. Align the tape in a horizontal plane, parallel to the floor.

Body Mass Index (BMI)

The BMI is commonly used to classify individuals as obsess, overweight, and underweight based off of their height and weight; it is also a tool to identify individuals at risk for obesity-related diseases; and to monitor changes in body fatness of clinical populations. (World Health Organization, 1998). It has been established that BMI is a significant predictor of cardiovascular disease and type II diabetes (Janssen et al., 2002) and because of that and the fact that BMI is easily calculated (body weight/body height squared); BMI is widely used in population-based studies. BMI is limited as an index of obesity because it does not take into account the composition of an individual’s body weight.

To measure body weight and height one should follow the following standardized procedures: (Gordon et al., 1988)

  1. When measuring weight use a beam scale with movable weights or an electronic digital scale and measure body weight to the nearest 100g.
  2. For measuring body weight, the client stands on the platform of the scale with the body weight evenly distributed between the feet. Light indoor clothing, but no shoes, may be worn. One trail is usually sufficient to obtain an accurate measurement.
  3. Use a standiometer with a fixed or movable rod to measure standing height. Height may be measured against a wall if the wall does not have a baseboard and the floor is not carpeted.
  4. The client is barefoot, stands on the flat surface that is at a right angle to the vertical rod or board of the standiometer. The weight is evenly distributed between the two feet, and the arms hang by the sides with palms facing the thighs. The heels of the feet are together with the feet being spread at a 60-degree angle to each other. The head is erect with eyes focused straight ahead.
  5. As the client inhales deeply, the horizontal board of the standiometer is lowered to the most superior point of the head, compressing the hair Measure height to the nearest 0.1cm.

Dual-Energy X-Ray Absorptiometry (DXA)

In the early 1980s, researchers used the method called duel-photon absorptiometry (DPA) to assess total body bone mineral (TBBM) [the total amount of body bone minerals] and bone mineral density (BMD) [a medical term normally referring to the amount of mineral matter per square centimeter of bones] (Peppler & Mazess, 1981). DPA used the reduction of photon beams from a radiated source to identity body tissues. In the 1990s dual-energy X-ray absorption (DXA) replaced DPA. DXA uses an X-ray tube instead of a radioactive isotope, thus improving the technology to provide greater precision and more accurate estimates of BMD and soft-tissue composition compared to DPA (Mazess et al., 1990).

The major assumptions for the DXA method focus on the estimation of the soft-tissue composition using this technology:

  1. The amount of fat over bone is the same amount as the amount of fat over bone-free tissue.
  2. Measurements are not affected by the anteroposterior thickness of the body.
  3. The hydration and electrolyte content of the lean tissue is constant.

The DXA method requires minimal cooperation from the client and technical skill. However, for precise and accurate DXA scans, proper training by the manufacturer in use of the scanner is essential. The general procedure is: (Mazess et al., 1990).

  1. Prior to testing, calibrate the DXA scanner using a known calibration marker provided by the manufacturer.
  2. Measure your client’s height and weight, with the client wearing minimal clothing and no shoes.
  3. Carefully position the client in the supine position on the scanner bed for a head-to-toe antero-posterior scan.
  4. Use a skeletal anthropometer to accurately determine body thickness.
  5. Set the scanner for a medium-speed whole-body scan, which usually takes about 20min.

Bioelectrical Impedance Analysis (BIA)

Bioelectrical impedance analysis is a rapid, noninvasive, and relatively inexpensive method for evaluating body composition in field and clinical settings. Thomassett’s (1962) pioneered the work in early 1960s which involved sending low-level electrical current through client’s body, and the impedance, or opposition to the flow of the current, is measured. An individual’s total body water (TBW) can be estimated from the impedance measurement because the electrolytes in the body’s water are excellent conductors of electrical current.

Movement Experiences

Body composition is related to success in executing motor skills; it serves as a structural constraint. For individuals who are overweight, it can also serve as a functional constraint. A body composition high in muscle mass and low in adipose tissue contributes to optimal performance. The muscle mass can be used to exert force, and low adipose tissue means a performer does not have extra weight to move, both of which constitute advantages in many physical activities. In contrast, a body composition that is high in adipose tissue can make it difficult to move the body, especially for extended times, and difficult to achieve certain body positions.


  1. Prior to body composition testing, inform the parents so they will understand the purpose and procedures of the assessment.
  2. Instruct the child regarding concepts and procedures for measuring body composition.
  3. Maintain records of these measures over time to assess the interaction effect of growth, maturation, diet, and physical activity on body composition changes.
  4. Measure only standardized sites and follow established procedures.
  5. If you feel it is necessary, ask the child’s parent to be present during the body composition testing.
  6. Ensure confidentiality by sharing test results only with the child and the parents.
  7. Provide personal feedback as interpretation results.
  8. Do not use body composition test result for grading results.
  9. Be sure to make the body composition assessment a positive experience for everyone. Do not label, criticize, or ridicule children during any phase of the assessment or after the assessment.
  10. Encourage children to play whether it is organized or not organized.


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