Lab 7 Flashcards
What can body composition be used for
Risk assessment, individualization of exercise regimens, and evaluating interventional progress
What is anthropometry
Measurements of the body
What is the calculation for body mass index
Weight (kg) / height (m^2)
Is BMI an accurate measurement of disease risk
Not for all individuals because there is no way to determine the composition of the weight (e.g. in weight-training individuals)
What does waist measurement aid in
Assessing central obesity to monitor the efficacy of weight loss programs
Is visceral (abdominal) or peripheral fat associated with greater health risk
Visceral (serves as independent risk-factor when BMI isn’t really increased)
What are indirect methods to assess body composition
Derived from direct methods using cadavers
What are double indirect methods to assess body composition
Derived from indirect methods
When will a population-specific equation be innacurate
When it is applied to people who differ in physical characteristics
How are generalizable equations derived
From diverse, heterogenous samples that account for differences in age, gender, race or ethnicity, etc.
What generalizable equation does lab 7 use to predict percent body fat
The Siri equation
Body fat % = (495/bone density) - 450
What is the SEE of skinfold measurements
~3.5%
The equations used to predict bone density from skinfold measurements use what method
Hydrostatic weighing (indirect method using water displacement to estimate fat mass)
What are the 2 primary assumptions in skinfold measurements
Subcutaneous fat is directly proportional to fat and skinfold sites are representative of total body subcutaneous fat
What factors can vary the proportion of subcutaneous fat to total body fat
Age, sex, race or ethnicity, etc.
What are 4 major limitations of skinfold tests
Training of technicians, application of equations, skinfold site measurement accuracy, and measurement technique
What principle is biometric impedance analysis (BIA) based on
Electric current flows at different rates through the body depending on its composition
What effect does body fat have on current flow
It causes resistance (impedance) that slows the rate the current travels
What does DEXA stand for
Dual-energy x-ray absorptiometry
What 3 chemical components do DEXA scans separate the body into
Lean soft tissue, fat soft tissue, and bone
Why is the percentage of body fat often higher using DEXA scans than anthropometric methods
Because DEXA scans measure not just subcutaneous fat but also retroperitoneal, visceral, and intramuscular fat
What do T-scores compare bone density to
Average bone density of healthy adults of the same sex
What do Z-scores compare bone density to
Average bone density of someone your same age, sex, and race/ethnicity
How does the risk for bone fracture change with bone density
Every SD below average BD doubles the risk of bone fracture
