## Re: Difficulty explaining VO2max

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• 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
Message 1 of 4 , Mar 1, 2009
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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

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).
• 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
Message 2 of 4 , Mar 1, 2009
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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

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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