3.15.08 Body Composition

Testing Order
1. Resting measurements- BP, HR, Gender, height, weight, age
2. BC-body comp. -a lot of sweating can increase margin of error.
3. CRF-GXT-warms you up
4. Muscular endurance- not if #3 was intense
5. Flex-flexibility (because you are warmed up

Body Composition (BC)
Our poor attempt to differentiate the makeup of the human body into two components.

Assumptions of Hydrostatic Weighing
Best way to estimate body comp. Can easily do it in a pool. Considered, arguably, the Gold Standard in estimating % body fat.
Criterion measure
skin fold calipers are the best Field test.

Valid-measures what it is supposed to. HSW is really estimating body density (Db)
To be valid, we have to take for granted certain assumptions:

1. Body weight can be divided into 2 components
a. fat mass (FM
-includes essential fat (need to live)
b. fat free mass (FFM)
-water(72%), protein(21%), mineral(7%)
-older adults-total body water decreases with age.
% H2O may be good for 18 yo but in a 70 yo their %H2O could be 68%.
-Bloating (retaining water) during cycle affects this too.

-ethnicity-African American muscle density is slightly higher than in whites.
difference in muscled vs. deconditioned

-osteoporosis, gender, age, AA and Hispanic have increased BMD while Asians have decreased BMD

2. The relative portion of H2O, protein, and mineral are constant between all individuals.

3. Density of FM= .901g/ml - this is a good assumption, fat is fat

4. Density of FFM = 1.10 g/ml
-differs specifically over ethnicity, higher in Native Americans

#s based on dissection of 4 white people
3 males, 1 female
young-within 20 years of each other
all died in traumatic car accidents
the woman's #s were so far off the males' that they threw her data out.

DEXA

Theory of Hydrostatic Weighing

1. Body density= Db = body weight on land/ body volume

-scale to measure BW
-hydrostatic weighting to measure BV.

2. BV=(wt. in air)-(wt. in water)
Archimedes Principle
reflection of H2O displacement
But muscle sinks, fat floats

therefore:

Db= wt. in air/[(wt. in air)-(wt. in water)]

RV: residual volume: always a certain amount of air in lungs after you exhale as much as you can. air wil make you float, making you less dense, thus seem to have a higher % body fat.

Skin fold technique (SKF)

Lange calipers: $200-250.

Estimating total fat mass
FM: visceral/ adipose: 2/3 of total body fat
subcutaneous: 1/3

SKF estimates subcutaneous fat stores so that you can extrapolate visceral also.

younger people store fat visceral fat differently than subcutaneous than older adults do. must take into consideration age.

Margin of error: + OR - 3-3.5%

ACSM pg. 62 box 42

Thigh- used commonly in both men and women.
find inguinal crease is the 0 mark
measure to the top of the patella
mark half way between.
grip above cross hairs 3in. apart perpendicular to fold. Reach from above.

Bicep/Tricep
common for females
0 mark on the chromium process-shoulder ridge end
measure to point of elbow

tri: mark bottom of tape measure
bi: mark above tape measure

Calf
from medial process of knee, let tape measure fall to 90 degrees. plum line down, measure at largest part of calf.

Abdomen
common site for all men, ethnic minority females
0 mark is all the bottom right corner of belly button, 2com over, 1cm down
finger is in the belly button

Superiliac (pelvic crest)
45 degree angle fold
ASIS (anterior superior iliac spine)
find hip pointer bone
measure from armpit straight over ASIS mark

Chest
o mark at armpit
measure to nipple
1/3 distance in females
1/2 distance in males
45 degree angle fold