Body Composition

Fat -free massBody Fat

essential non-essential

Further divide body into components

fatwaterbonemuscleorgan tissueother (nerves, connective tissue, etc)

Ideal Body Composition

healthaestheticsperformance

Healthy fat percentage

16-25% for females< 20% for males

Aesthetic body composition

lean look is prized and admireddesire can lead to eating disorders

Performance body composition

sport-specificsome sports have specific weight classes

wrestling, boxing, weight lifting

variability depends on the metabolic requirement of the activity and on the disadvantage of carrying extra weight

problems when individuals try to gain too much weight or lose too much

Measuring Body Composition

Two component models hydrostatic weighing (underwater) skinfolds

Multiple component models BIA DXA TOBEC Biochemical

Assumptions of measuring composition

dissection is most accuratemost indirect methods are based on

cadaver studiescadaver studies: small n (8), one femalefat mass 0.901 gm/mlfat-free mass 1.100 gm/ml

Cadaver studies

original work in 1940sdid not compare to other methods, just

direct measurementassumed density of 1.100 gm/ml

extrapolated to humans from guinea pigsuntil can validate a method directly, it is an

estimateall of the methods have limitations

Hydrostatic Weighing

Until DXA, most accurate methodbased on Archimedes’ Principle of water

displacement and densityprocedural difficulties

Dual Energy X-Ray Absorptiometry

developed to determine bone content and subsequently, density

may replace hydrostatic weighing as the gold standard

relies on fewer assumptions about human tissue

can use animals to directly validate the technique

Biochemical Techniques

potassium analysistotal body waterintert gas absorption

Anthropometric and Skinfolds

BMIWaist Circumference and Waist-Hip RatioSomatotypeAnthropometricSkinfolds

Ultrasound, Computerized Tomography (CT), and Electrical Impedance

ultrasound: technology used by cardiologists, estimate thickness of tissues

CT: x-ray that provides a three-dimensional view of the body

Total Body Electrical Conductivity (TOBEC): surrounds body with magnetic field and measures the rate at which the body conducts electrical energy

Bioelectrical Impedance Analysis (BIA): measure impedance to flow in opposite extremities