lectures 3-4 Flashcards
Body Composition Models
Anatomical or Fluid/Mineral
- 2-compartment Model
- FM
- LBM (FFM)
why is body comositon useful
- Sport Science
- Determine competition or race weight
- Assess & monitor growing athletes
- Monitor the effect of change to diet & exercise
- Medicine & public health
- Epidemiology of disease & body composition
- Detect atypical growth due to disease, eating
disorder, malnutrition - Concept of ideal body weight
- Child health, growth & development
Factors Affecting Body Comp
- genetic
- hormonal
- environmental
what is body fat for
Insulation
Thermogenesis
Energy
Skeletal tissue
Longitudinal skeletal growth has usually been completed by early adulthood Bones adapt to stress by increasing or decreasing Width Mineral density Architecture Skeletal mass accounts for ~23% of total mass in the adult
The effect of aging and fat and muscle
Fat levels tend to rise in both men &
women
Skeletal muscle & bone mass show an
age related decline (sarcopenia)
‘poverty of the flesh”
Reduction of LBM that appears to
accompany aging
why does age effect ageing
Reduced testosterone & HGH
Reduced physical activity
Malnutrition
Smoking
Assessing body composition
3 Levels Level 1 – Direct Level 2 – Indirect Level 3 – Doubly Indirect ○ (Martin & Drinkwater 1995)
Level 1 - Direct Assessment
Cadaver analysis – Anatomical Dissection Chemical: Fat Nitrogen Water Minerals Surface anatomy followed by dissection of each cadaver into gross tissue weights Anatomical: Skin Adipose tissue Muscle Bone Residual Results used to Develop new anatomically based models Test existing 2-compartment models
Level 2 - Indirect Assessment
Weight for height indices Hydrodensitometry Skinfolds Tissue fractionation Other techniques
Level 3 – Doubly Indirect
% body fat from Skinfolds Hydrodensitometry TOBEC BIA
Weight for height indices
Level 2 - Indirect Assessment
A measure of ‘ponderosity’ & often
incorrectly construed as ‘adiposity’
• BMI (W/H2) & Inverse ponderal Index (W/H1/3)
- Falsely assume any increase in weight beyond the normal/optimal level has to be
attributed to body fat!
Weight for height indices why is it used
Epidemiological validity ○ high correlation with adiposity in studies using large cross sectional samples Precision & reliability Ease of measurement Patient comfort
Hydrodensitometry - Level 2 - Indirect Assessment
- Measure body weight
Measure weight in water
Determine body density
skinfolds: Level 2 - Indirect Assessment
Measure compressed thickness of a double
layer of skin & subcutaneous tissue
Minimum 6 sites
O-Scale - Level 2 - Indirect Assessment
Does not predict body composition
Normative based system
Individual monitoring to provide feedbak
to client or athlete
Geometrical adjustment to standard stature
2 scales compared with same age & sex
DEXA – Dual Energy X-Ray Absorptiometry - Level 2 - Indirect Assessment
First developed to estimate bone mineral
density (BMD) of regions of the skeleton & more
recently whole body BMD
Uses a dual x-ray source of alternating pulses
Able to estimate body mass of the subject with
a high degree of accuracy
DEXA – Dual Energy X-Ray Absorptiometry limitations
Difficult to determine body composition in trunk region
Currently no cross-validation between machines
(different companies)
Siri’s equation for predicting% body fat from hydrodensitometry why is it unreliable
Tissue density is not constant:
Athletes tend to have denser bones & muscles
than non-athletes, which may lead to an
underestimation of body fat percentage.
Vice versa, body fat of elderly patients suffering
from osteoporosis may be overestimated.
Residual volume in the lung is not constant
% body fat from TOBEC & BIA - Level 3 - Doubly Indirect
Total Body Electrical Conductivity (TOBEC)
Examine electrical conductivity to estimate LBM
Bioelectrical Impedance Analysis (BIA)
regression equation with Ht & Wt as dominant factors
Both methods affected by variations in diet, hydration, ethnicity & disease states
% body fat from skinfolds - Level 3 - Doubly Indirect
More than 100 prediction equations developed using level 2 methods
Guerra et al (2010) used a regression equation to
convert SF data to body density, THEN used the
Siri equation to derive % body fat!
Population specific
If used at all, prediction equations must only be
used on similar populations to the original sample
Gaining weight
Gaining lean mass may be achieved without the need for drug therapy Create the correct stimulus Supply sufficient energy Provide adequate rest
Anthropometry used extensively for
- growth and development studies
- Predicting future capability (eg talent ID)
- Establishing selection criteria
Human proportions are measured using?
anthropometry
Measures include
Length & breadth
Girths & volumes
Assessing proportionality
Proportional indices
Somatogram
Phantom strategem
Assessing proportionality equations
Crural Index: CI = (leg length/thigh length) x100
Brachial Index: BI = (forearm length/arm length) x 100
Relative lower limb length: (lowe limb length/ stature) x 100
Crural index athelete examples:
low: LD runner
medium: sprint runner
high: basketball, volleyball
Brachial Index
low: weight lifter
medium: MD swimmer
high: Thrower
Relative lower limb length
low: gymansts, sprint runners
medium: thowers
high: MD runners, jumpers
The Somatogram
Graphical representation of the body’s proportions using girth measurements Measures a % deviation from the mean score in a population Each measure is plotted against the reference man/woman
