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The study I referenced earlier is listed below. There were
other data contemporary with this, by Steven Rerych for Duke, that was
substantially similar. I think the citation was Annals of Surgery, but
not sure without going to find it.
To get a VO2 of 6L, assuming 15 gm% hgb concentration, you have an a-v
O2 difference of 150 ml/L.
Therefore in terms of the Fick equation
VO2=CO*a-v O2difference
6000=CO*150
CO=40 L/min
CO=HR*SV=HR*EDV*EF
40000ml=200*EDV*0.8
40000=EDV*160
EDV=250 ml
This is a big heart, but not out of the range of what is reported (or
calculated ) from literature values.
More than a generation ago, the Swedes used green dye and reported
occasional CO values of 40 L/min in athletes.
Assuming a resting VO2 of 300 ml/min, a HR of 50, an EF of 0.6 and an
a-vO2 difference of 50 ml/L
300=CO*50
CO=6 L/min
6000 ml/min = 50*0.6*EDV
EDV=200 ml
Thus, in terms of the original question
HR*4
avO2 difference *3
EF*1.33
EDV*1.25
CO*4*1.33*1.25=6.65
SV*1.66
Reference
AnholmJD, Foster C, Carpenter J, Pollock ML, Hellman CK, Schmidt
DH: Effect of habitual exercise on the left ventricular response to
exercise. J Appl Physiol 52: 1648-1651, 1982.
Carl Foster
From:
sportscience@yahoogroups.com [mailto:sportscience@yahoogroups.com] On Behalf Of Ian Shrier
Sent: Sunday, March 01, 2009 6:13
AM
To: sportscience@yahoogroups.com
Subject: Re: Difficulty explaining
VO2max
I think
it is important that everyone remember that:
Cardiac output = HR * stroke volume
The ejection fraction is not in the equation.
Stroke volume increases if there is an increase in end-systolic volume
or a decrease in end-diastolic volume. The ejection fraction is simply
a function of these.
A normal heart has an ejection fraction above 60%. Ejection fractions
lower than 60% mean the person is starting to have heart failure.
Ejection fractions less than 50% are associated with increased
mortality and ejection fractions less then 40% represent moderate to
severe heart failure.
If you start at 60% ejection fraction, it is impossible to double it
to 120%. This is why Carl Foster said the most liberal estimate would
be from 60% to 80%. Note that this is a 33% increase and not a 60%-80%
increase as Catherine Bacon says below.
And of course, there is the increased a-v extraction noted by previous
answers.
So, to keep it simple, the increase in VO2max comes partly from an
increase in cardiac output (which comes because of a mix of an
increase in stroke volume and HR), and an and partly from an increase
in a-v extraction.
Of course, we don't usually exercise at VO2max so the changes with
exercise may be very different when exercising at VO2 max vs
submaximal exercise. I went looking for a table at VO2max but couldn't
get one online. Here is a table from a paper in JAP in 2009 in middle-
aged men cycling at 60-65% of VO2max. Note that most of the increase
in stroke volume does come from ejection fraction in this table, and
cardiac output increases are therefore due to HR and "ejection-
fraction related increases in stroke volume". At very high heart rates
experienced at VO2max, there is less time for the heart to fill, end-
systolic volume therefore decreases, and this leads to decreases in
stroke volume (not sure if ejection fraction declines but I think so).
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