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Physiology, Health & Exercise Lesson 15 zBody Composition & it’s Measurement.

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Presentation on theme: "Physiology, Health & Exercise Lesson 15 zBody Composition & it’s Measurement."— Presentation transcript:

1 Physiology, Health & Exercise Lesson 15 zBody Composition & it’s Measurement

2 2 Body Composition & Measurement Methods include: zDensitometry zSkinfold thickness zBioelectrical impedance analysis zBody Mass Index (BMI) zWaist/hip ratio zMid-upper arm circumference Limitations of each method

3 3 Body Composition zMeasuring someone’s mass does not tell us the whole story zi.e. doesn’t tell us much about their size or composition of their body z2 people can have the same mass but one can have more body fat & the other have less fat but more muscle zLevel of fat to muscle better indicator of how healthy someone is

4 4 Body Composition zNeed to determine ratio of fat to lean tissue (muscle, bone etc)  body composition zRemember do need some fat ycell membranes yFormation of some hormones yInsulation zJust not too much fat!! zIt is possible to lose fat from body & increase or maintain lean tissue  not much change in mass

5 5 Body Composition z% of body fat associated with the least health risk is y18-25% for females y13-18% for males

6 6 Body Composition Why is it important to assess body composition? 1.To assess the health risk associated with too much or too little fat 2.To monitor weight loss in an obese individual 3.To monitor changes in body composition associated with some diseases like cancer 4.To monitor the effectiveness of exercise training programmes in athletes

7 7 Body Composition How to measure? 1.Densitometry 2.Skinfold thickness 3.Bioelectrical impedance analysis 4.Body Mass Index (BMI) 5.Waist/hip ratio 6.Mid-upper arm circumference

8 8 Densitometry zFat is less dense than lean tissue zFat density is 0.9g cm -3 zFat-free tissue density is 1.1g cm -3 zIf measure density then can predict the relative proportions of lean and fat tissue in the body zVolume measured by Archimedes Principle! Density = mass volume

9 9 Densitometry zOnce density determined, % body fat is calculated as follows: zPerson A & B both have a mass of 60kg. Person A displaces 56.9 litres of water and B displaces 58.3litres. zCalculate % body fat for both zWho is overweight? % body fat = density

10 10 Densitometry- answer zPerson A has 19.42% body fat zPerson B has 30.97% body fat zPerson B is overweight

11 11 Densitometry- advantages zAccurate method

12 12 Densitometry- limitations zInvolves the person being totally submerged under water zMay be difficult & produce some anxiety zNew method developed using a “Bod Pod” which uses air displacement. zPerson sits in a small chamber and body volume calculated by measuring initial volume of empty chamber minus volume with the person inside zSpecialised equipment needed

13 13 Densitometry- Bod Pod

14 14 Skinfold thickness zMost widely used method zInvolves measuring the layer of fat under the skin (subcutaneous layer) at several specific sites zUses a skinfold caliper

15 15 Skinfold thickness z4 sites are commonly used: yOver the biceps at the front of the arm yOver the triceps at the back of the arm yUnder the shoulder blade at the back (subscapular) yAbove the hip bone at the side of the body (supra- iliac) zValues added and compared with values in table to predict body density & then body fat

16 16 Skinfold thickness- advantages zNon-invasive zRelatively cheap zPortable zQuick zAccurate once the skill has been mastered

17 17 Skinfold thickness- limitations zErrors associated with measurer skill zDoes not take into account unusual fat distribution zDifficult in the fat and very obese

18 18 Bioelectrical impedance analysis (BIA) zRelies on fact that fat is an insulator of electricity whereas fat-free tissue (approx 73% salty water) is a good conductor zInsulators have a higher resistance or impedance to the flow of a small electric current zGreater resistance  greater % body fat zElectrodes placed on the back of the right hand and right foot while subject is lying down

19 19 Bioelectrical impedance analysis (BIA)

20 20 BIA- advantages zRequires little or no technical skill by the operator zPortable zQuick- takes less than a minute to perform zOnly requires removal of a sock!

21 21 BIA- limitations zAny disturbance in hydration level (e.g. dehydration or oedema) will affect the accuracy of the results zChanges in skin temperature can also affect conduction of the electrical current zTends to overestimate body fat in very lean, muscular people and underestimate in obese people- so not as accurate

22 22 Body Mass Index (BMI) zMost commonly used index of over or underweight zUnits are kg/m 2 BMI = body mass height 2

23 23 Body Mass Index (BMI) ClassificationBMI (kg/m 2 )Associated health risks Underweight<18.5Low Normal average Overweight Moderate Obese class I Obese class II Obese class III > >40 Increased Moderately Severely Very severely

24 24 Body Mass Index (BMI)- caution! zClassification can result in an individual being classified as overweight or obese when have a relatively low % body fat, but large muscular bulk zE.g. body builders, weight lifters & other athletes with large muscle bulk yBody-builder with mass 130kg & height 1.90m would have BMI of 36.01kg/m 2 & be classed as obese class II

25 25 Body Mass Index (BMI)

26 26 Body Mass Index (BMI)- questions zTry the following questions: 1.Person A is 150cm tall & has a body mass of 65kg. What is her BMI? 2.What classification would she have? 3.How much weight would she have to lose for her BMI to be within the normal range? 4.Person B is 170cm tall and weighed 69kg. He recently lost 15kg on a diet. Explain how his BMI has changed & what could happen if he continues to lose weight.

27 27 Body Mass Index (BMI)- answers 1.Person A has a BMI of 28.9kg/m 2 2.She is moderately overweight. 3.She would have to lose 9kg 65 - (24.9 x 1.5 x 1.5) 4.At start B has BMI of 23.9kg/m 2  normal After weight loss BMI is 18.7kg/m 2  close to underweight which could have a negative impact on his health

28 28 BMI - advantages zEasy to calculate

29 29 BMI- limitations zCan lead to wrong classification as does not differentiate between high % fat and high % muscle zImportant to differentiate between large muscle bulk and excess fat

30 30 Waist/Hip ratio zThe distribution of fat in the body rather than total quantity is more important zPeople classed as apples (android) or pears (gynoid) zApples  extra abdominal fat (“pot-belly”)- have a higher risk of CHD, diabetes etc zPears  extra fat around the hips & thighs

31 31 Waist/Hip ratio

32 32 Waist/Hip ratio zUse a measuring tape to check the waist and hip measurements. - Measure your hip circumference at it's widest part. - Measure your Waist Circumference at the belly button or just above it.Waist Circumference zUse the same units for both! zRepeat 3 times and take an average

33 33 Waist/Hip ratio zFor women 0.8  pear shape & > 0.8  apple zFor men 1.0  pear shape & > 1.0  apple zAt risk values are > 1.0 for men & > 0.8 for women

34 34 Waist/Hip ratio zIt is possible to have a high BMI and a normal waist measurement if you are a fit, lean, muscular man. This is why your waist to hip ratio is a better guide to your risk of heart disease.

35 35 Waist/Hip ratio - advantages zBetter estimate than BMI for some zEasy to calculate zRequires little equipment

36 36 Waist/Hip ratio - limitations zTakes no account of body composition

37 37 Mid-upper arm circumference zIs the circumference of the left upper arm, measured at the mid-point between the tip of the shoulder and the tip of the elbow

38 38 Mid-upper arm circumference - advantages zEasy to calculate zRequires little equipment zEasy to perform zQuick to carry out

39 39 Mid-upper arm circumference - limitations zBetter for estimating under-nutrition zLack of data upon which to decide useful cut- off points zchanging patterns of skeletal muscle and subcutaneous fat as people age

40 40 Your mission….. Work out your body composition using the following methods: 1.Skinfold thickness 2.Body mass index 3.Waist/hip ratio 4.Mid-upper arm circumference zRecord 1 & 2 on your personal profile sheet zMake a comment on your observations


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