Body composition

body composition

1. BODY COMPOSITION Mihir Baria 1 ST Year MPT

2. What is body composition? Body composition describes the relatives proportions of fat, bone, muscle mass in the human Body. Body composition = Body is relative amounts of fat free mass and fat mass. It refers to the body’s chemical composition. There are 3 models of body composition:: 1.chemical model 2. Anatomical model 3.Two compartmental model.

3. In Fat, Two type of fat 1 .Essential fat ::(Male- 3 to 6% , female= 8 to 12% of body mass) Essential fat consists of fat in the heart, lungs, liver, spleen, kidneys, intestines, muscles, and lipid-rich tissues of the central nervous system and bone marrow. Normal physiologic functioning requires this fat. 2. Storage fat:: accumulate in adipose tissue

4. Why we need Body composition analysis Body composition and analysis provides information about % of body fat, fat distribution, body segments girth. How much fat lose versus how much muscle to gain? Which are participant to athletic performance and for reducing risk factors associated with Musculoskeletal injury and disease.

5. Assessing Body Composition Five level Multi component model to assess and interpret body composition::

6. Two method Direct method Indirect method Direct method Chemical solution dissolves Physical dissection

7. Assessing body composition (indirect method) Height, weight, BMI W- H ratio Hydro densitometry Air displacement method Skin fold method Girth measurement Bioelectrical impedance analysis Ultrasound DEXA

8. Height,weight and BMI Height:: it is measured by Stadiometer Weight :: it is measured by Weighing scale. BMI:: measured by following equation BMI= Weight / (Height)² Weight in kg Height in m

9. Waist Hip ratio The WHO STEPS protocol recommends that the subject stands with arms at the sides, feet positioned close together, and weight evenly distributed across the feet. The measurement be made at the approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest(waist circumference), waist circumference should be measured at the end of a normal expiration, when the lungs are at their functional residual capacity. The hip circumference measurement should be taken around the widest portion of the buttocks(Hip circumference) W hich calculates the ratio of your weight to your height, WHR measures the ratio of your waist circumference to your hip circumference. It determines how much fat is stored on your waist, hips, and buttocks. It’s indicate body fat distribution patterns. According to the  World Health Organization  (WHO), a healthy WHR is: 0.9 or less in men 0.85 or less for women

10. Hydrodensitometry Densitometry:: Measuring the density of the body. Density is defined as mass divided by volume: D=M/V M=mass of body( measured by scale weight) V= volume of body(measured by 1. hydrostatic weighing 2.Volume also measured by air displacement techniques. Densitometry has long been the technique of choice for assessing body composition.

11. Hydrostatic weighing Underwater weighing Most common method to assess body volume Person’s compare regular weight with underwater weight. Hydrostatic underwater weighing is based on the Archimedes’ principle. This principle states that the amount of liquid a submerged object displaces is equivalent to the volume of the object. By measuring your weight on land and your weight underwater, test administrators can calculate your body’s density Density= Weight on land ÷ weight in water (1 g of water = 1 cm³ by volume at 39.2F)

12. Procedure Prior to the hydrostatic weighing, you’ll likely be instructed to avoid exercising or eating for at least 4 hours beforehand. Here’s what to expect during the procedure: 1. The test administrator measures and records your body weight on land. 2. You then slowly enter a water tank that has an underwater seat hanging from a scale. 3. Your testing administrator instructs you to completely submerge underwater while sitting on the chair and to breathe out fully. 4. You repeat the test three times. The administrator will use the average result of the three tests to calculate your body fat percentage.

13. Draw back of hydrostatic weighing Time consuming Difficult to perform on the aquaphobic Requires measurement of residual lung volume Practically not possible to test large number of people.

14. Air displacement method BOD POD, A plethysmography device used to assess body volume. When subject is enter in to the chamber that time reduce the air volume. The subject sites in a structure composed of two chamber each of known volume. A molded fiberglass seat forms a common wall separating the front and rare chambers. A volume perturbing element connects the two chambers. Change the pressure between two chambers oscillate the diaphragm, which directly reflects any change in the chamber volume. The subject make several breaths into the air circuit to assess thoracic gas volume.(which when subtracted from measured body volume yields true body volume)

15. Densitometry has its limitations, if body weight, underwater weight and lung volume during underwater weighing are measured correctly, the resulting body density value is accurate. The equation most often used to convert body density to an estimate of relative and percentage body fat is the standard equation of siri % body fat= (495/ D) – 450 (D= Body density) Mass of body fat calculated by Fat mass(kg)= body mass(kg)×(percentage fat÷100) Fat free mass is measured by FFM(kg)= body mass(kg) – fat mass(kg)

16. Skinfold Measurements Simple anthropometric procedure to measure body fat is skinfolds. Skinfold to estimate the body fat composition results from the close relationship among three factors Subcutaneous fat in adipose tissue deposits directly beneath the skin body’s internal fat store body density of the intact human body

17. The caliper accurately measured Subcutaneous fat at selected body sites. Three different types of skinfold caliper. 1. Harpenden: The Harpenden Skinfold Caliper is a precision instrument designed for use in the performance of Skinfold thickness measurements, The Harpenden Skinfold Caliper has been used all over the world on projects of international importance and is the most prestigious Caliper available. 2 .Lange: These calipers feature spring-loaded arms providing a constant standard pressure of 10 gm./sq.mm 3. Common plastic:  The device consists of a vernier scale – metric as well as inch measurement - with a fixed and a movable jaw Measuring skinfold thickness requires grasping a fold of skin and subcutaneous fat firmly with the thumb and fore fingers and pulling it away from the underlying muscle tissue following the skinfold’s natural contour. The skinfold is recorded within 2 seconds after applying the full force of the caliper.

18. Skin fold sites triceps – vertical Subscapular – oblique Iliac crest – oblique Abdomen – vertical Thigh – vertical Biceps - vertical

19. Girth measurements Six most common sites for girth measurement. Girth offer an easily administered and valid alternative to skinfolds. Apply a linen or plastic measuring tape lightly to the skin surface so the tape remains taut but not tight, avoid skin compression.

20. Predicting body fat from girth From the appropriate tables in Appendix C, substitute the corresponding constants A, B, and C in the formula shown at the bottom of each table. This requires one addition and two subtraction steps. The following five-step example shows how to compute percentage fat, fat mass, and FFM for a 21-year-old man who weighs 79.1 kg: Step 1:: Measure the upper arm, abdomen, and right forearm girths with a cloth tape to the nearest 0.25 in (0.6 cm): Upper arm =11.5 in (29.21 cm); abdomen = 31.0 in (78.74 cm); right forearm =10.75 in (27.30 cm). Step 2:: Determine the three constants A, B, and C corresponding to the three girths from Appendix C: Constant A corresponding to 11.5 in = 42.56; constant B corresponding to 31.0 in =40.68; and constant C corresponding to 10.75 in = 58.37

21. Step 3:: Compute percentage body fat by substituting the appropriate constants in the formula for young men shown at the bottom of Chart 1 in Appendix C as: Percentage Fat =Constant A + Constant B - Constant C -10.2 = 42.56+40.68-58.37 –10.2 = 83.24-58.37 – 10.2 = 24.87 – 10.2 =14.7% Step 4:: Calculate the mass of body fat as: Fat mass =Body mass (% Fat /100) = 79.1 kg ×(14.7 / 100) =79.1 kg × 0.147 = 11.6 kg Step 5:: Determine FFM as: FFM = Body mass -Fat mass =79.1 kg - 11.63 kg = 67.5 kg

22. Bioelectrical impedance Analysis(BIA) Bioelectrical impedance analysis  ( BIA ) is a commonly used method for estimating  body composition , in particular body fat and muscle mass or for weight loss goal. In BIA, a weak electric current( 1-10 μ A ) flows through the body and the voltage is measured in order to calculate  impedance  (resistance) of the body. Most body water is stored in muscle. Therefore, if a person is more muscular there is a high chance that the person will also have more body water, which leads to lower impedance. Bioelectrical impedance analysis devices are considered safe for most people. However, BIA should not be used by anyone with an electronic medical implant, such as a heart pacemaker or an implantable cardioverter defibrillator (ICD). Also, most device makers recommend that the products not be used by pregnant women.

23. Some factors that may affect a reading when you use a BIA scale.  Body weight.  Bioelectrical impedance analysis may be less accurate in obese people. Hydration level.  Dehydration may cause fat-free mass (muscle and bone) to be underestimated. Recent exercise activity.   High-intensity exercise  may affect the accuracy of BIA readings. Recent food or drink intake.  some study suggest that BIA may be more accurate after overnight fasting.

24. Ultrasound Assess the thickness of different tissue. Obtain an object of deeper tissue such as a muscles cross sectional area The method converts electrical energy through a prob into high frequency sound waves that penetrate the skin surface in to the underlying tissues. The sound wave pass through the adipose tissue and penetrate the muscles layer and then reflect from the fat muscle interface after the reflection from a bony surface to produce an echo,which return to a receiver within the probe.

25. Dual-Energy X- Ray Absorptiometey Dual-energy x-ray absorptiometry (DXA),a high-technology procedure shown in Figure to assess bone mineral density in osteoporosis screening can also quantifies fat and muscle around bony areas of the body, including region without bone present. When used for body composition assessment, DXA does not require assumptions about the biologic constancy of the fat and fat-free components as does hydrostatic weighing. Two distinct x-ray energies with short exposure with lowradiation dosage penetrate into bone and soft tissue areas to a depth of about 30 cm. Specialized computer software reconstructs an image of the underlying tissues. The computer generated report quantifies bone mineral content, total fat mass, and FFM. DXA also can target selected body regions for more in-depth analysis.

26. OTHER LABORATORY TECHNIQUES Many other laboratory techniques are available for assesing body composition. Near Infrared interactance CT scan MRI

27. Reference Essentials Of Exercise Physiology (Old) by William D. McArdle BS M.Ed PhD,  Frank I. Katch  , et al. Physiology of Sport and Exercise by  W. Larry Kenney  , Jack H. Wilmore, et al