Week 10 - Body Composition Assessment Methods Flashcards
Health related importances of body composition assessments
ID clients health risk associated w/ excessive low or high levels of total body fat + lean mass.
Promote clients understanding of health risks associated w/ too little or too much body fat + lean mass
Monitor changes in body comp that can improve the cond of clinical pop.
Understand + improve self-esteem + confidence at different life stages
Performance related importances of body composition assessments
ID optimal lean mass + fat mass to achieve high level perf.
Monitor growth, development + maturation in relation to body comp + athlete development
To formulate + implement effective exercise + nutrition interventions aiming to improve body comp components.
Categorise groups based on specific ref standards
Give a direct method of body composition measurement
Chemical analysis of carcasses
Example study of a direct method of body composition measurement
Brussels Cadaver Study
Carried out in vivo neutron activation + chemical analysis using radioactive isotopes.
The monitored specified the vol + densities of all tissues by weighing them underh20
Example study of a direct method of body composition measurement
What did the chemical analysis find?
- 6% H20
- 5% Protein
- 9% Minerals
INDIRECT METHODS
What densitometry methods are there for estimating body fat %
Hydrodensitometry
ADP (Air-displacement plethysmography)
DXA (Dual Energy X-ray Absorptiometry)
How is body density (Db) calculated?
Mass / Volume
kg/L
What are the assumptions in densitometry
Fat comp = 0.9 g/ml
FF comp = 1.1 g/ml
What does the fat comp include
Adipose + neural + essential fat
What does the fat free comp include
Lean mass
Bone mass
Tendons
Organs
H20
What does Archimedes’ principle state
A body immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body.
What is the error of method for hydrodensitometry
±2.5% if done w/ experienced participants.
What are inaccuracies in hydrodensitometry due to?
Variation in the density of FFM from 1 ind to another.
Age, sex + race affect the density of FFM.
What are the sources of error for hydrodensitometry
Not getting all air out
Reading scales wrong
Not using correct equation
Estimation of residual vol.
What does hydrodensitometry form
The 2C model of FM + FFM.
Determines body vol by displacing H20 + directly measuring change in H20 vol.
How is vol of H20 displaced calculated in hydrodensitometry
Body weight - (underH20 body weight / water density)
Equation to calculate body density in hydrodensitometry
Db = Wa / [(Wa - Wtw) / Dw] - (RV + Vgi)
Wa = Body weight in air Wtw = Body weight in H20 Dw = Water density (~1 g/mL) RV = Residual Vol Vgi = Air in GI tract
What is body density in H20 affected by?
Air in body
Can’t remove air from lungs in hydrodensitometry so what happens instead?
We determine residual vol + air in GI tract (~0.1L)
Equations to determine residual vol
Males
0.24 x VC
( 0.019 x height (cm) ) + (0.0115 x age ) - 2.24
Equations to determine residual vol
Females
0.28 x VC
( 0.023 x height (cm) ) + (0.021 x age ) - 2.978
Advantages of hydrodensitometry
Valid, reliable + widely used
Specific equations to each group
Predictive error is 1-2% or less body fat when RV is measured
Disadv. of hydrodensitometry
Time consuming
Ambulatory problems
Can be uncomfortable to blow all air out
What does Air-displacement Plethysmography (ADP) / BOD POD measure
Body vol through air displacement.
Measures pressure changes w/ injection of known vol of air into closed chamber.
— The large body vol displaces air vol in chamber to result in bigger ⬆️ in pressure w/ injection of known vol of air.
Boyles law
Pressure + vol of a given mass of confined gas are inversely proportional.
Adv to Air-displacement Plethysmography (ADP) / BOD POD
Subject acceptability
Precise
Less time consuming than hydrodensitometry + req less technical skills
More accommodating + available
Disadv to Air-displacement Plethysmography (ADP) / BOD POD
Expensive - £20-25k
Assumes that it controls the isothermal effects of clothing, hair, thoracic gas vol…
Assumes constant density of FFM + FM for pred of % body fat from whole body density
Why is Dual Energy X-ray Absorptiometry (DXA) a multi compartmental model
Has 2 different energy level x-rays
Dual Energy X-ray Absorptiometry (DXA)
Lean, fat + bone mass each reduce the x-ray signal for each point in the image + calculated by direct comparison standards.
How is the Dual Energy X-ray Absorptiometry (DXA) a clinical relevant device
For the assessment + diagnosis of osteoporosis
What results does the Dual Energy X-ray Absorptiometry (DXA) provide you with?
whole body + site specific results
Give examples of doubly indirect methods
BMI
Circumferences + girths
Skinfolds
Bioelectrical impedance analysis
List some anthropometric methods
Circumference/girth
Bony diameters
BMI
Waist:Hip
Waist:Height
Sagittal Abdominal Diameter (SAD)
What do anthropometric prediction equations estimate?
Db
%BF
FFM
Adv of Dual Energy X-ray Absorptiometry (DXA)
Accurate + considered the ‘Gold Standard’
Clinical measurement of osteoporosis
Quick + safe
Minimal subject cooperation
Low radiation exposure
Disadv Dual Energy X-ray Absorptiometry (DXA)
Expensive - £35-40k
Limited Access
Result may vary w/ model, software version…
What type of measure is the Waist:HIP (WHR)
Indirect measure of fat distribution
Calculated as: Waist circumference (cm) / Hip circumference (cm)
What is an issue with Waist:HIP (WHR)
Location of waist isn’t universally standardised.
Which men are at high risk for adverse health consequences based on Waist:HIP (WHR)
w/ WHR values >0.94
Which women are at high risk for adverse health consequences based on Waist:HIP (WHR)
w/ WHR values >0.82
Diasdv Waist:HIP (WHR)
WHR of women is affected by menopausal status — postmenopausal women show more of a male pattern of fat distribution than premenopausal women.
Not valid for evaluating fat distribution in pre-pubertal children.
Accuracy of WHR in assessing visceral fat decr as fatness incr.
Hip circumference is influenced by ONLY subcutaneous fat whereas waist by visceral + subcutaneous fat. — WHR may not accurately detect changes in visceral fat accumulation.
Waist:Height (WHTR)
Could be a better indicator of adiposity + health risks than waist circumference alone.
What is the general rule for Waist:Height (WHTR)
Waist circumference should be less than half the height.
What is the cutoff boundary value of WHTR due to indicating an incr. health risk
WHTR>0.50
Adv of BMI
Quick to calculate + don’t need technical knowledge
Widely used to predict CV disease + type 2 diabetes
Basic equipment needed
Not expensive
Disadv of BMI
Doesn’t count for composition of the body
Possible misclassification
Other anthropometric indices need to be used to assess fat distribution
BMI cutoff to define obesity may not be appropriate
What does Sagittal Abdominal Diameter (SAD) measure
Visceral obesity
Amount of fat in gut region
What do the Sagittal Abdominal Diameter (SAD) results indicate
<25cm = Normal BMI
> 30cm = incr. risk of coronary disease
% BF Siri (1961) equation
(4.95 / Db - 4.50) x 100
% BF Brozek + colleagues (1963) equation
(4.57 / Db - 4.142) x 100
Adv of the SKF method
Measures subcutaneous fat
Useful for large groups
Portable
Not expensive - £10-500
Validated vs hydrodensitometry method
Disadv of SKF method
Pressure differences in different callipers
Subject factors i.e compressibility of SKF
Prediction equation - Valuable only for the population that were used to derive them
What is needed to ensure low intra-testing + inter-testing technical error of measurement ?
Training
What must the intra-tester be?
<10% iSAK
What must the inter-tester be?
<12.5% ISAK
What are population specific %BF equations based on?
Linear relationship between SKF fat + Db (linear model)
Where is there a curvilinear relationship?
(Quadratic model)
Between SKFs + Db across a large range of body fatness.
When might using population specific equations underestimate %BF?
In fatter subjects
When might using population specific equations overestimate %BF?
In leaner subjects
What assumptions are there in the SKF?
Fat patterning
Relationship between internal + external fat
Skin thickness
SKF compressibility
Lipid fraction of adipose tissue
H20 content of adipose tissue
What does the Bioelectrical Impedance Analysis (BIA) measure
Impedance by body tissues to the flow of a small alternating electrical current (<1mA)
What is impedance a function of?
Electrical resistance of tissue
Electrical storage of tissue (reactance)
BIA frequencies
Low freq
(50kHz)
Don’t have enough energy to pass through cell walls easily
BIA freq
What are lower freq better suited to measuring?
Extracellular H20
BIA freq
High freq
Can measure intra + extracellular H20
Suited to penetrating cell walls
What are the 3 major types of BIA analysers
Omron
Tanita
Bodystat
What do Omron BIA devices measure?
ONLY impedance in arms + upper body
Direct Segmental Multi-free BIA (DSM-BIA)
Analyse body in 5 distinct sections independently:
- 2 arms
- 2 legs
- torso
Adv to BIA
Portable + convenient
Quick test time - 5 mins
Privacy not compromised
Rel cheap - £250-1000
Beginning to develop specific equations - can get resistance value from machine + enter into a specific equation
Disadv to BIA
Accuracy + precision is affected by changes in body H20
Sensitive to body temp
Lower precision than DXA + ADP/ BOD POD
Tends to overestimate body fat in very lean muscular ppl + underestimate % fat in obese
Typical BIA Equations
Females FFM
(-9.53 + 0.69xHt^2) / (R + 0.17xW + 0.02 x R)
W = Body weight (kg) R = Resistance (ohms)
Typical BIA Equations
Males FFM
(-10.68 + 0.65 x H^2) / (R + 0.26 x W + 0.02 x R)
W = Body weight (kg) R = Resistance (ohms)
What do girths measure + how?
Measure impedance by body tissues to flow of a small alternating electrical current (<1mA)
Where should the measuring tape be held when taking girths
Perpendicular to limb or body segment being measured.
List the sites for measuring girths
Waist Hip Mid-abdominal Neck Arm relaxed Arm flexed & tense Calf Max forearm Mid thigh Max upper arm
Location for taking waist girth
“Stand erect w/ abdomen relaxed, arms crossed at chest + feet together.
Measurer faces subject laterally + places tape measure around subject in horizontal plane at level of natural waist. “
Location for taking hip girth
“Stand w/ arms crossed at chest + feet together in anatomical position.
Measure squats at side of subject so level of max width of buttocks can be seen.
Tape measure is placed around buttocks in horizontal plane at this level w/out compressing the skin. “
Location for taking mid-abdominal girth
Taken at level of the naval.
Location for taking neck girth
Taken inferior to larynx w/ tape
Location for taking arm relaxed girth
Circumference of arm at level of midacromialeradiale site.
Subject is standing in relaxed position w/ arms by side. Right arm - slightly adducted to allow tape to be passed round the arm.
Location for taking arm flexed + tense girth
“Circ. of arm perpendicular to long axis of arm at level of peak of contracted biceps brachial when arm is raised anteriorly to the horizontal.
Subject raises right arm anteriorly to horizontal w/ forearm supinated + flexed at 90 degrees.
Subject is requested to partially contract their bicep + tape is placed over largest part.
When taking reading, subjects is asked to fully contract bicep + largest circumference is recorded. “
Location for taking calf girth
“Circ/ of calf at site of medial calf SKF.
Subject stands erect, feet 10cm apart + weight evenly distributed; measurer crouches to right side + moves tape up + down calf perpendicular to long axis until greatest circumference is located. “
Location for taking max forearm girth
“Max circ. at proximal part of forearm (usually w/in 5cm of elbow).
Subject stands erect w/ arm extended in horizontal place w/ hand supinated; measurer stands behind arm + moves tape up + down forearm until max circ. is located. “
Location for taking mid thigh girth
“Girth taken at midpoint between trochanterion + tibiale lateral.
Subject stands erect, feet 10cm apart + weight evenly distributed, measurer stands to right side, palpates + marks trochanterion + tibiale lateraled.
Midpoint is found using tape, girth is taken at that level, perpendicular to long axis of thigh. “
Location for taking max upper arm girth
”
Girth measurement of upper arm at insertion of deltoid muscle.
Subject stands erect w/ arm abducted to horizontal, measurer stands behind arm of subject, marks insertion of deltoid muscle + measures girth perpendicular to long axis of arm. “
In Air-displacement Plethysmography (ADP) / BOD POD what does a smaller body vol result in?
Less ⬆️ in pressure
Why can accurate estimates of skeletal muscle mass be made using BIA?
Due to skeletal muscle being an electrolyte-rich tissue
What anthropometric equations would you use to calculate muscle mass
Matiegka (1921) (in vitro derived equation)
Lee et al. (2000) (in vivo derived equation)
Martin et al. (1990-MALES ONLY) (in vitro derived equation)
What BIA equation would you use to calculate muscle mass
Janssen et al. (2000) (in vivo derived equation)
What equation do you use to calculate average muscle mass
Lee et al. (2000) (in vivo derived equation)
What anthropometric equations would you use to calculate skeletal muscle mass?
Matiegka (1921) (in vitro derived equation)
Drinkwater et al. (1986) (in vitro derived equation)
