Hydroweigh Flashcards
underwater weighing procedure is based on what?
Archimede’s Principle
Archimede’s Principle
an obj buoyed up by a force equal to the weight of the water displaced, an object displaces its own volume in water
Based on AP how do we know weight
force buoyed up the object = weight of displaced h20
density of water
1 g/cc
how do you calc body density?
divide person weight in grams by their weight minus their weight in water
Body mass in air is measured to the nearest
1/quarter pound using a medical platform scale
Body weight is then converted to body mass assuming
2.2 lbs of body weight is = 1 kg of body mass
body mass in air is expressed in
grams
The subject will sit in a specially designed chair suspended in a stainless steel tank filled with
warm water after they have been removed from the suit and skin
What tool/device is used to insure total submersion of the subject ?
a weighted S.C.U.B.A. belt
First trial/ one trial consists of the subject forcefully exhaling as much air from lungs as possible, pulling what to do what
head to knees to fully submerse the entire body, and remaining still until a signal is received to return to the surface
Who issues signal and when?
The signal is issued by the technician performing the test when the total mass of the system has been determined to the nearest 50 grams using Chatillon autopsy scale.
What happens if there are fluctuations in the scale?
If fluctuations in the scale due to movement of the subject are encoutered, the midpt of the range of values observed is recored as the total mass in the water
How many trials are completed ?
5 or more depending on the consistency of the measurements
What values are used for body mass in water?
The mean of the two highest measures of body mass in water is used.
Body mass in water is expressed in?
grams
The vital capacity (VC) is measured to the nearest
50 mL
How is the subject positioned for Residual Lung volume (RV) test?
The subj is seated in a position similar to that assumed under the water.
AIrflow through nose is prevent by
having the subj wearing a noseclip
One trial of RV consists of the subject
inhaling maximally, placing the mouthpiece of the spirometer into the mouth, sealing the lips around the mouthpiece, and forcefully exhaling all air from the lungs
How many trials?
3 to 5 trials are performed depending on the consistency of the measurements
What is used from RV test to get VC?
The mean of the highest 2 volumes is used as VC
RV is estimated by assuming it to be a
constant proportion of the measured vital capacity, and poprotions based on data from Wilmore, 1969.
RV is expressed in
mL
Male RVbtps=
(0.24xVCatps)10001.063
Female RVbtps =
(0.28 x VC atps) * 1000*1.063
Water density is measured in blank or blank
g/ml or g/cc
Body density formulae equation of
goldman and buskirk 59
DB =
MA/[MA-MW]/DW - RVbtps
DB
body density (g/cc)
MA
body mass in air (g)
MW
body water in water (g)
DW
Water Density (g/ml)
RV
Residual lung volume in BTPS (ml)
MW =
water weight- tare weight
MA=
lbs/2.2 = kg *1000 = g
%Fat = eqn for femalses
[(4.57/DB)-4.142]* 100
Fat weight =
body weight * (%fat/100)
Lean weight=
Body weight- fat wt
