Body composition

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In physical fitness, body composition is used to describe the percentage of fat, bone, water and muscle in the human body. Because muscle tissue takes up less space in our body than fat tissue, our body composition, and our weight, determines the level of sainthood. Two people with the same gender and weight may look very different because they have different body compositions.

Video Body composition

Body density

The most accurate estimate of body composition comes from the density of the body by means of a fractional density equation which states that the overall density of the mixture containing more than one substance (each with different density) can be calculated if the proportions and densities of each substance are known. For the determination of body composition the body is often assumed to consist of four basic substances ("four compartment models") with the general form of the equation as follows:

${\ displaystyle 1/Db = w/Dw f/Df p/Dp m/Dm}$

Di mana: ${\ displaystyle Db}  ÂÂ$ = kepadatan tubuh keseluruhan, ${\ displaystyle w}  ÂÂ$ = proporsi air, ${\ displaystyle f}  ÂÂ$ = proporsi lemak, ${\ displaystyle p}  ÂÂ$ = proporsi protein, ${\ displaystyle m}  ÂÂ$ = proporsi mineral, ${\ displaystyle Dw}  ÂÂ$ = densitas air, ${\ displaystyle Df}  ÂÂ$ = kepadatan lemak, ${\ displaystyle Dp}  ÂÂ$ = kepadatan protein, ${\ displaystyle Dm}  ÂÂ$ = kepadatan mineral

In a research laboratory setting, the whole body density (Db) is calculated from its mass and volume (Db = mass/volume). Body mass is discovered only by weighing a person on a scale. The easiest and most accurate body volume is determined by fully immersing a person in water and calculating the volume of water from the weight of the moved water (through "underwater weighing"). The proportion of water, protein and minerals in the body is found by various chemical and radiometric tests. The density of water, fats, proteins and minerals is measured or estimated. This equation is then rearranged to complete the fat proportion (f) of the other quantity.

Accurate body fat estimates can be obtained using the two compartment models of the human body based on two simplifying assumptions: 1. Human fats have a density of 0.9 grams/ml, and 2. Fat (nonfat) components of the human body have overall density of 1.1 gram/ml.

Both compartment models allow for estimation of the proportion of body fat and lean components made from overall body density. And, as described above, the overall body density (Db) is easily calculated from body mass and body volume. Rearranging the fractional density equation to solve the fatty proportion (f) will yield the following equation:

${\ displaystyle f = 495/Db-450}$

The human fat density is very constant in all subgroups studied but variation has been reported in fat-free mass density (ie, lean or non-fat components). To overcome this difference, a unique equation for two compartment models has been proposed for a particular population.

Maps Body composition

DEXA

Measurements of body composition with dual energy X-ray absorbents (DEXA) were used increasingly for various clinical and research applications. The DEXA scan requires medical supervision by radiologists and some consider it a new "Gold Standard" in testing body composition. Total body scan using DEXA provides accurate and precise measurements of body composition, including bone mineral content (BMC), bone mineral density (BMD), lean tissue mass, fatty tissue mass, and fractional fat contribution.

Estimates of body fatness from body density (by weighing underwater) were accepted as a "gold standard" for decades. Some researchers now claim that the whole body scan technique (eg "DEXA") is the new "gold standard". However this claim is somewhat dubious because the scanning algorithm is validated against the assessment of body composition based on the fractional density of the underwater weighing.

DEXA measurements can be highly reproducible if the same type of machine is used (referral), making it excellent for monitoring pharmaceutical therapy, nutrition or exercise interventions, sports training and or other body composition change programs. They are also fast, simple, non-invasive, and expose the subject to less x-ray levels than cross-country flights. The DEXA exam provides total body and up to 14 regional results (body, individual arm & leg, android, gynoid, etc.). However, the role of DEXA in clinical evaluation and research has been questioned by Wang et al. which states that "the error of the DXA [DEXA] method is still a concern if it will be used as a criterion."

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Plethysmography air movement

Another technique for measuring body composition has been developed to measure body volume using different methods of underwater weighing. This technique uses air as opposed to water and is known as water displacement plethysmography (ADP). Subjects enter a closed space that measures their body volume through air movement in the room. Body volume combined with weight (mass) to determine body density. This technique then estimates the percentage of body fat and lean body mass (LBM) through empirically derived equations similar to those used with underwater weighing (for fat-free and fat-free mass density).

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From the conductivity

Another method is bioelectrical impedance analysis (BIA), which uses electrical resistance through the body to estimate body fat. Unfortunately, BIA is very sensitive to hydration status and water intake. Drinking water dilutes the electrolyte in the body so it is less conductive as does increasing body fat.

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Skin folds

Body composition can also be measured using a skin-bending test, performed using a device called a caliper. This can be done in nine steps:

1. Make a measurement on the right side of the body.
2. Mark clients.
3. Pinch skin (KM) above the
mark
4. Drag the fat from the muscle
5. Place the half caliper between the top and bottom of the
mark
6. Allow calipers to complete (1-2 seconds)
7. Read - repeat 15 seconds
8. Add the total (4) - average
9. Calculate body fat%

The common skin-fold method is to use a rifle-style caliper to measure the thickness of subcutaneous fat in some places of the body. These include abdominal areas, subscapular areas, arms, buttocks and thighs. This measurement is then used to estimate total body fat.

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Ultrasound has also been used to measure subcutaneous fat thickness, and by using some estimates of body composition points can be made. Ultrasound has the advantage of being able to also directly measure muscle thickness and measure intramuscular fat.

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Circumference and other measurements

Somatic assessment (skeletal) proteins are usually determined by simple measurements and calculations including mid-arm muscle circumference (MAM), and high creatinine (CHI) ratios. The creatinine high ratio was calculated as 24-hour urine creatinine multiplied by 100 times greater than the estimated 24 hours of urine creatinine for height. The results of these calculations are in percentages that can indicate protein depletion.

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Validity

The above methods are each valid and important in providing a fairly accurate range of "true body compositions" of the individual being tested. However, each method does have its own limitations, indeed preventing the existence of so many variable methods available for an individual to use. Therefore, actual body composition testing methods are not as important as measurement consistency between each test. (See internal consistency for excellence in testing in this way.) If an individual is tested from one period to the next, all ideally factors remain as close as possible to reflect the best indicators of the correct composition change.

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Type of exercise

The exercise required to maintain optimal body composition differs from one man to another, but the ideal type of fitness remains the same.

The main exercises needed to improve body composition involve fat burning and cardiovascular exercise.

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See also

• Body volume index
• Body Mass Index

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References

Source of the article : Wikipedia