Body Composition Flashcards
Body composition focuses on techniques to measure…
- body fat
- lean body mass
- fat free mass
Direct body composition:
- chemical analysis
- cadaver analysis
Indirect body composition:
- hydrostatic weighing
- skinfolds
- BIA
- etc.
Body composition is the separation of ____ ____ into _____ _____.
- bodily tissues
- quantifiable compartments
____ compartment model is most common.
2
2 compartment model divides body into:
- fat vs FFM (essential
- fat removed) or lean body mass (includes essential fat)
Nonessential fat is….
adipose tissue
Essential fat is….
intra organ/muscle/other tissues
FFM and LBM includes…
- muscle
- bone
- organs
- etc.
Fat has a density of _____g/ml.
0.900 g/ml
FFM has a density of ______ g/ml.
1.100 g/ml
Why can there be error with 2 compartment model?
assuming fat and FFM density
Multiple compartment models:
models that account for more than 2 body compartments
The greater number of body compartments accounted for, the greater the…
reduction of error
Example of multiple compartment model:
- Dual Energy X-ray Absorptiometry (DEXA)
- 3 compartments: fat, soft tissue, bone
- the measurement of bone density significantly reduces the error associated with amount of variation in bone density among individuals (aging)
Hydrostatic weighing is based on _____ ____.
Archimedes’ Principle
Archimedes’ Principle:
- any object immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object
- not to be confused with the volume of fluid displaced by an object
For hydrostatic weighing, we must know….
- residual volume
- density of water
- trapped gas (GI)
- dry body weight
- submerged body weight
Residual volume is calculated based on…
- height
- age
- sex
Density of water varies with _____.
temperature
Trapped gas (GI) is approximated to be ____ mL.
100 mL
Dry body weight is with…
- minimal clothing
- minimal trapped air
Submerged body weight is with…
- same clothes
- minimal trapped air
Minimum equipment required for hydrostatic or underwater weighing technique:
- body of water
- accurate hanging scale
- thermometer
- water density table/calculator
- may need weights to assist with submersion
- body density (BD) calculation
BD =
dry weight / [((dry weight - wet weight) / water density) - total gas volume]
Procedure for hydrostatic weighing:
- full end expiration and submersion for 5-10s
- minimize movement
- repeat 5-10 times
Several formulas have been derived by a variety of research to predict _____ from BD.
% body fat
% body fat can be used to calculate…
- fat mass (kg)
- lean body mass (% or kg)
Siri (1961):
% fat = (4.95/BD) - 4.50 * 100
Brozek (1963):
% fat = (4.57/BD) - 4.142 * 100
Lohman (1986):
% fat = (5.3/BD) - 4.89 * 100
Limitations of hydrostatic weighing:
- assumption of the constant density of body fat and LBM
- assumption of the magnitude of trapped air: GI tract, lung, body cavity
- variability in body mass determination
- number of trials performed
Possible ____% (_____) error in body fat prediction is possible due to the variability in the density of ____ ____ ____ in women.
- 19% (relative)
- LBM
Possible ____% (_____) error in body fat prediction based on the variability in ____ volumes alone.
- 8% (relative)
- lung
How is variability in body mass determination a limitation?
in air, things such as hydration/dehydration, nutritional status can influence calculation
Accuracy of hydrostatic weighing is enhanced if ____ trials are done.
9-10
Hydrostatic weighing: if all factors are carefully controlled, repeated measurement of % fat from UW varies approx _____.
- +/- ~3%
- range 2.5-3.8%
Reliability of hydrostatic weighing:
- can be good
- test/retest r = 0.98
In hydrostatic weighing, there is limited ____ measurements done, so ____ is difficult.
- direct
- validity
Hydrostatic weighing as an _____ measure is considered to be ____.
- indirect
- valid
BodPod is aka…
air displacement plethysmography
BodPod uses the same theory as ____ _____, but uses ____ _____.
- hydrostatic weighing
- air displacement
BodPod is _____.
automated
In BodPod, we need to minimize ____ _____ (…) but not full _____.
- air displacement (clothing, swim cap)
- expiration
BodPod can be used in many _____.
populations
BodPod: Concurrent validity with UWW:
r = 0.94
BodPod: test-retest reliability:
r = 0.96
DEXA =
Dual Energy X ray Absorption
DEXA is a 3 compartment model:
- lean soft tissue
- fat soft tissue
- bone
DEXA uses a ____ type of radiation to scan the whole body, and can provide ____ data with respect to fat distribution.
- low
- regional
DEXA: inter-day reliability:
r = 0.90 to 0.99
DEXA: concurrent validity with UW:
r = 0.90
DEXA: claim is that the error is less than ____% for fat.
~3%
Limitations of DEXA:
- relatively expensive
- need technical certification (Alberta) to operate
- due to radiation, cannot be used in some populations (pregnancy)
- can only accommodate individuals of a certain size
- metallic implants will interfere with measurements
- other radiological tests may interfere with measurements/results
MRI assumes a __ compartment model:
- 3
- lean soft tissue
- fat, soft tissue
- bone
MRI uses a high frequency ____ ____ to ____ molecules.
- magnetic field
- vibrate
MRI can provide very fine ____ (____) data with respect to fat distribution.
spatial (regional)
____ is the most accurate determination of body composition.
MRI
MRI is considered by many as the new ___ ____.
gold standard
Limitations of MRI:
- very expensive
- limited accessibility
- limitations with respect to size of individuals (bone diameter)
Skinfolds measure…
the thickness of fat-folds including the skin at various sites around the body that can be anatomically land-marked
Skinfolds can be used as a ____ of various sites and can be used in a formula to predict ____ or ____ ____.
- sum
- % fat
- body density
Major assumptions of skinfolds:
- the choice of sites are representative of total body fat
- subcutaneous fat is related to total body fat
Skinfolds: Equations for predicting body fat generally work 2 ways:
- sum of skinfolds is directly entered into a formula that predicts % fat
- sum of skinfolds is entered into a formula to predict body density, then can be used in same formulas as hydrostatic weighing for predicting % fat
Limitations of skinfolds:
- need consistency with respect to land-marking of site and amount of fat pinched
- time taken to read measure and finger pressure
- # of sites measured for sum or prediction of % fat formula
If all factors are carefully controlled: % fat from skinfolds varies approx. ___% but is usually higher.
+/- 5%
Skinfolds is recommended using techniques that include ____ and ____ _____ skinfolds.
upper and lower body
Variability in skinfolds:
type of caliper used and jaw tension
3 types of calipers:
- Harpenden
- Lange
- Slim guide
A ___% difference between Harpenden vs Lange calipers has been reported.
10%
Skinfods: spring load of jaw should be ___ gm/mm^2.
8-10
Skinfolds are a ____ ____ method.
doubly indirect
Are skinfolds reliable?
can be depending on technique
Skinfolds test retest reliability of …
r =
Skinfolds are not recommended for…
- people with BMI greater than 30
- otherwise can be used with a variety of individuals
BIA:
bioelectrical impedance
Advantages of BIA:
- easy to use
- non-invasive
- practical
- fast
BIA uses …
a low level electrical current
BIA measures the _____.
impedance (opposition to current flow)
BIA: since water/electrolytes conduct ____ ____ with ____ impedance, tissues with more water (eg. ___) have _____ opposition to current flow.
- electrical current
- less
- muscle
- lower
BIA: the greater the resistance to current flow, the greater the….
- fat content
- since fat has lower water/electrolyte content
Limitations of BIA:
- numerous assumptions many of which may be questionable
- requires strict adherence to pre-test guidelines
- validity is questionable
- reliability is varied r = 0.66-0.94
- different manufacturers use different formulas for determining % fat
BIA: pre-test guidelines:
- no eating or drinking within 4 hours of test
- no exercise within 12 hours
- must urinate within 30 minutes
- no alcohol within 48 hours
- no diuretic type medications within 7 days
- no testing at certain days of the menstrual cycle
- body position important, arms away from sides, legs apart/not crossed
Near-infrared interactance measures….
- optimal density of near-infrared light of 2 wavelengths for the bicep of the dominant arm
- at the 2 wavelengths used, fat absorbs light and LBM reflects light
With near-infrared interactance, a ____ measures the difference between….
- sensor
- amount of light emitted and reflected back
Near-infrared interactance uses formulas that have a variety of _____ to predict % fat.
assumptions
Near-infrared interactance has ___estimation of body fat up to ___% and is worse in _____ clients.
- underestimation
- 10%
- obese
Near-infrared Interactance: _____ is questionable; ____ can be good.
- validity
- reliability
Both CSEP CPT and AFLCA CFT recommend ____ and ____ to evaluate anthropometrics as opposed to _____ _____.
- BMI
- WC
- body composition
What factors should be consider when choosing which techniques to use?
- consider validity and reliability of technique
- application with respect to performance or health
- practicality and cost
- risk
Anthropometrics and body composition may be changing naturally in some populations such as…
- normal development and maturity
- pregnancy
With children, _____ growth can be calculated with respect to population based _____.
- standardized
- means
With children, ____ indicate how many ____ a value is from the mean.
- z-scores
- standard deviations
Children: ______ represent where a values places with respect to the entire _____.
- percentiles
- distribution
PHV:
- peak height velocity
- the maximum rate of growth in stature during the growth spurt
PHV is determined using charting of…
- height
- sitting height
- arm span
PHV can be used by ____ for tracking ____ ____ of children and allows _____ of training fitness components around _____.
- coaches
- developmental age
- planning
- growth
Formula to predict maturity offset:
how long until (or after) a child reaches PHV
Age of PHV =
age + maturity offset
Weight by height ratio =
(weight/height) * 100
Pregnancy: when excess weight is gained, most of the excess will be laid down as ____ ____ and ____ ____.
- body reserves
- heavier baby
Body composition is very important for ___ ____ (___) and _____ (_____).
- general population (health)
- athlete (performance)
Consider _____, _____, _____ etc. if selecting formula-based outcome measurements.
- population
- age
- gender
Consider if anthropometrics/body comp are dynamic based on _______.
population (children/pregnancy)
Consider ____ data availability.
normative
Report ____ with measurement.
variability
Ensure good _____.
technique
Do not succumb to technology without ____ _____.
research support
