Anthropometry and Body Composition PDF

MEDI221 Body Composition  Lecture Objectives Describe measures of anthropometry & body composition Discuss anthropometry and body composition in the context of health and sports. Discuss the pros and cons of different methodologies for assessing anthropometry and body compositi...

MEDI221 Body Composition  Lecture Objectives Describe measures of anthropometry & body composition Discuss anthropometry and body composition in the context of health and sports. Discuss the pros and cons of different methodologies for assessing anthropometry and body composition Text Book: McArdle, Katch & Katch Chapter 28 Terminology Anthropometry: Standard techniques to quantify or predict body size, shape and proportion Body Density: Body Mass (BM) per unity body volume Fat Mass (FM): All extractable lipids from adipose and other body tissues Body Mass= FM + Fat Free Mass (FFM) Lean BM (LBM)= FFM + essential fat DEXA/DXA= dual-energy x-ray absorptiometry Simple Anthropometric Measures Height Body Mass/Weight Volume (e.g. girths) Waist Circumference Somatotype SOMATOTYPES Sheldon 1940s – description of Physique Graded on a scale of 1-7 (1=low, 7 = high) from ecto, meso and endomorphy Served previously as a simple but mostly ineffective methodology to analyse meaningful differences in physiques between athletes and familiar heritabilities Simple Anthropometric Measures Height Body Mass/Weight Volume (e.g. girths) Waist Circumference Somatotype Body Mass Index (BMI) BMI = Body mass (kg) / height2 (m) i.e. 60 kg/ 1.682 = 21.3 Optimal BMI is 20-25 kg/m2 BMI and Mortality – Is it this simple? Large population studies have shown that a “healthy BMI” is Your Turn: between 20-25kg/m2 Why might BMI not - Can you identify flaws in this be a true generalization? representation? Body Composition Really important for body composition to take into account Lean Mass which is really important for health related indices BMI is always used in epidemiology because we cannot give everyone a DEXA scan! Some Body composition measures that take into account % fat and muscle (lean mass): DEXA- gold standard BIA- bioelectrical impedance (gyms) Under-water weighing (body density) BodPod (air displacement) DEXA – imaging Gold Standard Most common multi-tissue imaging method Rationale: Fat, bone and protein tissues scatter and transmit energy beams differently (due to different densities and chemical compositions), more so at low than high energy. Pros: highly accurate (typical error ~1-2%), can distinguish between regional and central body fat Cons: Highly specialised and expensive BIA- Bio-impedance Rationale: FFM mainly water (~73%) and electrolytes, which conducts current really well- compared to fat. Bioimpedance is a measure of how well the body impedes electric current flow. Fat has high resistance to the current Blood has lower resistance to the current. Needs standardised conditions: If dehydrated (hypohydration)- ↑ impedance- ↑ calculated fat If too warm – sweat- ↓ impedance - ↓ calculated fat Menstrual cycle (fluid shifts) Cant be used with pacemaker Pros: Quick, convenient Cons: Medium accuracy (~4%), possibly less accurate for obese Under Water Weighing Hydrostatic Underwater weighing Total body displacement (Archimedes principle of displacement) Archimedes Principle of Displacement: Buoyant force on a submerged object is = to the weight of fluid that is displaced by the object. Previously the gold standard Pretty much obsolete due to new methods Process Person first weighed on land  Sitting on a special scale lowered into a large tank of water  Asked to expel all air from lungs and remain still  Underwater weight is measured  Process repeated 3 times & averaged  Special calculation then used to determine body composition Pros- accurate, consistent Cons- person performing test needs to be trained, know how to do calculations properly, subject to person expelling all air from lungs, need a massive tank of water, expensive  BodPod (Air Displacement) Pros: accurate, can detect small changes in body composition, comprehensive report, quick, easy to perform Cons: expensive ~$110 000USD, need to ensure the same conditions each time tested due to equipment sensitivity. Source: https://child-health-research.centre.uq.edu.au/about/services-and-facilities/body-composition- Source:=https://www.bing.com/videos/search?q=bodpod&&view=detail&mid=9E4805F57AE13A laboratory/body-fat-and-calorie-testing-adults/bodpod®-test-information-and-pre-test-requirements 7CF7C59E4805F57AE13A7CF7C5&&FORM=VDRVRV Other Techniques Skin Folds- measure skin thickness from ~7 sites and calculate FM based on several assumptions Cons: doesn’t do LBM or FFM For the 4 body composition measures make sure you know: the rationale the pros/cons the accuracy  Why is measuring body composition and body type important? Health Sports Performance https://www.boredpanda.com/athlete-body- types-comparison-howard-schatz/ Body Composition Summary Anthropometry is used to assess techniques to quantify or predict body size, shape and proportion Body composition and anthropometric measures can be used to stratify risk of disease Somatotyping is an older method for qualifying body composition and anthropometry and is sometimes used to select potential athletes There are many methods for assessing anthropometry and body composition and all have pros and cons for their use and accessibility In sports, certain body types have been linked to sports that may provide an advantage but not in all cases