How menopause affects athletic women A sumo wrestler is a good illustration of subcutaneous fat deposited around the waist.
The Physician and Sportsmedicine, 14 3 Assessing Body Composition The search for valid methods of measuring body composition that are practical and inexpensive is an ongoing process for exercise scientists and nutritionists. Standard age-height-weight tables derived from life insurance data often incorrectly indicate individuals to be overweight.
Some practical methods of measuring body composition include skinfolds, circumference girth measures, hydrostatic weighing, bioelectrical impedance, and near-infrared interactance.
Other advanced methods discussed in research journals include isotope dilution, neutron activation analysis, magnetic resonance imaging, and dual-energy x-ray absorptiometry. This error factor may be increased dramatically due to the skill or lack of it of the technician taking the measurements.
The following sections will focus on three body fat measurement techniques that are often accessible to fitness professionals: Hydrostatic Weighing Hydrostatic weighing is a valid, reliable and widely used technique for assessing body composition.
It has been labeled the "Gold Standard" or criterion measure of body composition analysis. It is based on Archimedes' principle. This principle states that an object immersed in a fluid loses an amount of weight equivalent to the weight of the fluid which is displaced by the object's volume.
This principle is applied to estimate the body volume and body density of individuals. Since fat has a lower density than muscle or bone, fatter individuals will have a lower total body density than leaner individuals. As the person is being submerged, the air in the lungs must be exhaled completely.
The air remaining in the small pockets of the lungs following a maximal expiration is referred to as the residual lung volume. The residual lung volume may be determined using a number of laboratory techniques or it is often estimated using age, height, and gender-specific equations.
Once your body weight, the underwater weight, and the residual lung volume are known, total body density may be calculated. From the total body density, the percent body fat can be estimated using the appropriate age-gender equation.
One limitation of hydrostatic weighing is that it is based on the two- component model fat and fat-free mass which assumes when calculating total body density that the relative amounts and densities of bone, muscle, and water comprising the fat-free mass are essentially the same for all individuals, regardless of age, gender, race or fitness level.
It is now known that this is not the case.
For instance, the fat-free body density of young Black men is greater than that of white men. Because of this, the lean body mass is overestimated and the body fat is underestimated for many Blacks. Also, after age 45 to 50, substantial changes in bone density, especially in women, invalidate the use of an assumed constant value for fat-free body density when converting total body density to percentage of body fat.
This is why age and gender specific equations need to be used for estimating body fat. As researchers learn more about age-related changes in bone mineral, hydrostatic weighing will eventually provide a more accurate prediction of body fat for older men and women. Bioelectrical impedance analysis BIA is based on the fact that the body contains intracellular and extracellular fluids capable of electrical conduction.
A non-detectable, safe, low-level current flows through these intracellular and extracellular fluids. Since your fat-free body weight contains much of your body's water and electrolytes, it is a better conductor of the electrical current than the fat, which contains very little water.
So this technique is essentially an index of total body water, from which fat-free mass is estimated. The popularity of the BIA method has grown significantly over the last few years because it is painless, quick, and easy to administer the test.
To take the test, you lie on a testing table or floor and electrodes are attached to your hands and feet. You do not feel a thing as the current passes through your body. Average time for administering this test is about 10 minutes. No eating or drinking within 4 hours of the test 2. No exercise within 12 hours of the test 3.
Urinate within 30 minutes of the test 4. No alcohol consumption within 48 hours of the test 5. There is a tendency for BIA to overestimate percent body fat in very lean clients and underestimate body fat in obese clients.
All in all, if the guidelines for testing are followed, the BIA method is a satisfactory method for assessing body composition of most people. Skinfold Method The skinfold method of measuring body fat is a practical, economical, and administratively feasible field technique for body composition analysis.
It involves measuring the skinfold subcutaneous fat thickness at specific sites of the body. Most equations use the sum of at least three skinfolds to estimate body density from which body fat may be calculated.As with most opinions, this piece too is not % correct.
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