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Exercise Physiology > Final - Body Composition Methodology > Flashcards

Final - Body Composition Methodology Flashcards

1
Q

Body composition assessment is quantification of what body structure components?

A

muscle (protein)
bone
fat
water (body fluid compartments)

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2
Q

Overweight

A

a body mass greater than some standard (usually for a given stature)

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3
Q

Overfat

A

body fat greater than a standard for sex and age (requires body composition analysis)

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4
Q

Is it possible to be overweight without being overfat?

A

yep

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5
Q

Essential fat

A 
bone marrow stores & stores in viscera and nerves 
- needed for normal function
- 3% in males
- 12% in females
Includes sex-specific fat
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6
Q

Storage Fat

A
  • accumulation of lipid in adipocytes
  • nutritional reserve
  • subcutaneous and visceral (intraperitoneal)
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7
Q

Lean Body Mass (LBM)

A

includes essential fat, muscle, water, bone, mineral

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8
Q

Fat-Free Mass

A

All lipid contributions excluded

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9
Q

BMI and obesity classification

A

20-24.9: desirable
25-29.9: Overweight (grade 1 obesity)
30-40: Grade 2 obesity
>40: grade 3 obesity

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10
Q

Average % fat in young adults:

A

Men: 12-15%
Women: 25-28%

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11
Q

Overview of Body Composition Methodologies

A
  • Hydrostatic weighing
  • Skinfolds
  • Bioelectric Impedance Analysis
  • Imaging Technologies
  • Air Displacement Plethysmography (bod-pod)
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12
Q

Overview of Densitometry

A

Measure Body Volume (hydrostatic weighing, skin folds, bod-pod) + measure body mass on a scale
mass/volume = density
conversion equation from density to %fat (Siri, Brozek)
Yields estimate of % fat

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13
Q

Hydrostatic Weighing

A
  • 2 compartment body composition model of FFM and fat
  • Goal: estimate body density (d=m/v)
  • We have mass, we need body volume
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14
Q

Body Density

A

g/cm3 (mass per unit volume)

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15
Q

Fat and FFM have different densities

A
  • Fat-free body tissue: 1.100 g/cm3

- fat in adipose tissue: 0.900 g/cm3

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16
Q

How does hydrostatic weighing work?

A
  • determines body volume by Archimedes’ principle
  • object placed in water is buoyed up by a counterforce equal to the water it displaces
  • Amount of water displaced (spillover) equals loss of weight completely submerged
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17
Q

When using hydrostatic weighing, what must you taken into account?

A

air in lungs and GI tract

failture will overpredict %fat

18
Q

Calculation of body density from underwater weight

A
19
Q

Population specific formulas to calculate % body fat from body density all have some error bc of biological variability

A
  • bone mineral density
  • partitioning and volume of water
  • mineral components of the FFM
20
Q

Siri’s Equation

A

% body fat = (495/D) - 450

21
Q

Brozek’s Equation

A

% fat = (457/D) - 414.2

22
Q

Hydrostatic Weighing Validity

A

when residual volume is actually measured, hydrostatic weighing is the standard to which other methods are compared (within 2.0% of true value)

23
Q

Advantages of hydrostatic weighing

A
  • highly reproducible
  • can be highly accurate
  • valid for many populations (except small children and those who won’t be submerged)
24
Q

Disadvantages of Hydrostatic Weighing

A
  • best accuracy in highly technical experienced labs
  • bulky equipment
  • methodological concerns (prediction of RV, accuracy of weighing procedure, subject cooperation)
25
Q

Skinfold Thickness Anthropometric Measurement

A
  • relies on the observation that within a certain population, a certain fraction of total body fat lies just under the skin (prediction of total body fatness from subcutaneous fat)
  • skin fold thickness highly correlated with % body fat
26
Q

Most important variables contributing to measurement error in Skinfold measurements

A

investigate technique and experience

reproducibility and accuracy

27
Q

Methodology for Skinfolds

A
  • sites can vary (triceps, subscap, suprailiac, abdominal, thigh, chest)
  • Measurement duration is very important
  • reading should be taken within 2 seconds of applying caliper jaws
28
Q

Skinfold Caliper

A

Best results are obtained with a specifically- calibrated skin fold caliper

  • constant tension exerted by spring loaded caliper jaws
  • tension exerted affects how much extracellular fluid is pushed out of the area
29
Q

Prediction equations for skin folds

A
  • choose equation develop and verified for subjects demographic
  • subcutaneous fat to total body fat ratio is altered with age and sex
  • failure to use appropriate equations can introduce huge errors into the estimate of density and % BF
30
Q

Sum of Skinfolds

A
  • helpful for following weightless in an individual

- in obese individuals, it may be more accurate to use prediction equations that use circumferences than skin folds

31
Q

Advantages of Skinfolds

A
  • inexpensive and quick - mass screening
  • good for following changes in body comp
  • fairly reproducible and accurate in experienced hands
32
Q

disadvantages of skin folds

A
  • population specificity in prediction equations can lead to large error
  • error highly dependent on investigator technique
  • caliper used should be the same used in prediction equation
33
Q

Bioelectrical Impedance Analysis

A
  • noninvasive, fast, accessible, relatively cheap method to evaluate body composition
  • determines electrical impedance of body tissues (measures opposition of tissues to flow of small alternating electrical current and provides estimate of total body water)
  • less impedance in FFM (due to greater electrolyte concentration)
34
Q

BIA estimates FFM and body fat from TBW from predication equations that use what?

A
  • impedance
  • weight
  • height
  • sex
  • age
35
Q

BIA accuracy

A
  • reliable estimate of TBW under most conditions
  • limited ability to predict body fat in severely obese
  • not useful in measuring short-term changes in body composition
  • significant differences in % fat prediction between manufacturers
  • different prediction equations used
  • accuracy equivalent to skin fold technique if protocol is followed
36
Q

Standard recommendations for BIA

A
  • attempt to maintain normal hydration, plasma osmolality, body fluid distribution
  • dry skin
  • no eating/drinking within 4 hrs, exercise within 12 hrs, alcohol within 48 hrs, diuretic agents
  • void before assessment
37
Q

Near-Infrared Interactance

A
  • uses amount of light absorption vs reflection: typically at a single site to predict body fat, uses prediction equations
  • not for human body composition analysis currently
38
Q

Air-Displacement Plethysmography (Bod-Pod)

A
  • similar to hydrostatic weighing, it is densitometric
  • body volume directly measured
  • body density and % body fat calculated using same equations used to HW
39
Q

Bod Pod vs Underwater Weighing Advantages:

A
  • Fast (5 mins)
  • Can use with various populations (obese, elderly, pediatric)
  • Good compliance ( no need for maximal exhalation or immersion, mobile)
  • less operator training required
40
Q

Body Composition Assessment Sources of Error:

A
  • measurement error (intra and inter-investigator error)
  • subjectivity (training and experience)
  • fixed equipment or machine error
  • Underlying assumptions error (constants, models and predictive equations used, estimates of physiological variables, **normal biological variability)
  • experimental conditions (hydration status, subject cooperation, environment)

Exercise Physiology (17 decks)

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