Slide 6 - Air Displacement Flashcards

1
Q

Air displacement is what type of model

A

Two component model of body compositon

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2
Q

What is the equation for body density

A

Mass / volume

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3
Q

How is volume determined

A

By air displacement

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4
Q

What does the BodPod have to determine the amount of air displaced by the person

A

Pressure sensors

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5
Q

What law is the relationship between pressure and volume

A

Boyles Law

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6
Q

What does Boyles Law estimate

A

Body volume

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7
Q

Boyles Law states

Equation

What do we have to assume

A

Volume and Pressure are inversely related

P1V1 = P2V2
or
P1/P2 = V2/V1

Isothermal conditions

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8
Q

What is the methodology behind the air displacement

A

Isothermal conditions = Temp of air remains constant as its volume changes

Majority of the air in the enclosed bod pos is under Adiabtic conditions

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9
Q

What is adiabatic conditions

A

Temp of air does NOT remain constant as volume changes

Thus it will compress or expand as the temo changes within the chamber

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10
Q

What is the Poissons Law equation

What does it state

A

P1/ P2 = (V2/V1) v

The ratio of the specific heat of the gas at constant pressure to that of constant volume

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11
Q

What is the Body volume equation

A

Body volume (L) = Body volume (raw) - surface area artifact + 40% TGV

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12
Q

What does TGV stand for

Where is it measured

A

Thoracic gas volume

In the BodPod

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13
Q

What is the equation for body density

What equation do we use to estimate body fat %

A

Body mass / body volume

Siri equation

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14
Q

How do we minimise isothermal effect

A

Wear minimal clothing

Men:
Speedo etc

Women:
Form fitting clothing

Wear swim cap

Near skin surface

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15
Q

How long does it take for the BodPod to calibrate

A

30 min warm up for electronics

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16
Q

What does the BodPod have to go through in order to have good quality control

A

Analyze hardware
Calibrate scale
Autorun
Volume check - calibration cylinder

2 point calibration before each client

17
Q

What are the pre test measures of BodPod

A

No exercise, food or drink 3 hours before

Use restroom before test

Measure body mass 1 time

Measure body volume 2-3 times

Select daily activity level

Measure/predict TGV

18
Q

How do you work out TGV

A

FRC + 1/2 TV

19
Q

What errors may occur with BodPod

A

Airway pressure - high if puff too forcefully

Merit - high if air leaks

20
Q

When assessing body composition of each client in the Bod Pod, a 2-point calibration is performed by measuring the empty chamber of Bod Pod and the chamber with a 50 L calibration volume cylinder (and breathing tube) placed inside

21
Q

Like hydrostatic weighing, the Air Displacement Plethysmography using Bod Pod assesses body composition by determining the density of the body

22
Q

When using Bod Pod, correct height and weight measurements are needed to calculate body surface area

23
Q

Exhaling to maximal expiration is necessary to obtain an accurate measure of body fat when using the Air displacement plethysmography

24
Q

The air inside the chamber expands or is compressed as the temperature in the chamber changes describes isothermal conditions

25
How does the Air Displacement Plethysmography assess body composition
By measuring changes in pressure within an enclosed chamber
26
Air displacement plethysmography measures ______ component(s) model of body composition
2
27
You are a 30 year old woman with body weight of 85.6kg and height 167.2cm. % body fat was determined using Bod Pod and it was 35%. Your current lean body mass is
85.6 x 0.65 = 55.64 Kg
28
You are a 30 year old woman with body weight of 85.6kg and height 167.2cm. % body fat was determined using Bod Pod and it was 35%. If you want to reduce body fat to 28%, what is your target weight
85. 6 x 0.65 = 55.64 | 55. 64 / 0.72 % = 77.3 kg
29
Your result from Bodpod showed that your % body fat was 10.5% while DXA result showed 10.6%. This indicates that _____ regarding measurement concept
Air displacement plethysmorgraphy is a VALID technique to ASSESS body composition
30
Air displacement plethysmography using Bodpod follows Boyle's law because of the isothermal condition that the body creates in the chamber
False
31
Air displacement plethysmography using Bodpod follows Poisson's law because of the adiabatic condition that the body creates in the chamber
True
32
Using Bodpod, body volume can be underestimated if your thoracic gas volume is higher than what it is
False