Jiri Thanks here a long awaited feedback. For more in depth interested readers see the picture in the att word document. and come back with critics and questions.
Thanks so much for your great thoughts.
I like to start with the end.
I love the study out of different reasons.
“This protocol, using VO2max rather than power as the controlling variable, demonstrates that the maintenance of exercise at VO2max can exceed 15 min independent of the VO2max value, suggesting that the ability to sustain exercise at VO2max has different limiting factors than those related to the VO2max value”
It is soooooooo nice to see, that we slowly get accepted publications accepting the fact, that VO2 whether we talk about VO2 max or VO2 peak or VVO2 is really the summary of a whole “ team” of physiological systems” who all need and work with O2 to keep alive. The fact , that we slowly move from the dark black idea of VO2 as something absolute to the bright side on inside view in who contributes to the overall performance and how is the O2 distributed to get to this performance.
1. This protocol,
using VO2max rather than power as the controlling variable.
When we started 30 years back to argue, that we should use a physiological bio marker to control intensity rather than power or speed we got some interesting faces looking at us.
We argued during a sport conference, that there is no such thing like a heart rate drift. It is only something like a performance drift.
Meaning , that when we use a stable value of a bio marker like HR or like RF to take a few simple examples, or in Billat's case VO2 max, or a fixed VO2 value, than we will have a performance drift.
So when using a fixed HR we will see a drop in performance over time instead of a drift in HR. Same when using RF.
Same as Billat points out we have a drop in performance , when trying to keep VO2 stable.
In contrary if performance stays stable and if we are in a STEI intensity we can afford to drift HR and SmO2 as we have some compensatory mechanism but we drift into another training intensity and as such have a different stimuli than possibly planned.
See South Africa study by Mark
She than points out :
ability to sustain exercise at VO2max has different limiting factors than those related to the VO2max value .
Different limiting factors.
I would argue that there are different compensatory factors together with limiting factors.
The increase in time on VO2 max wills challenge more blood distribution into the working muscles, but as well a needed control of body temperature and so on.
The change in blood distribution for temperature condole for example takes blood out of the circulatory system and as such will decrease the cardiac preload due to less return of blood. Depending on the limiter at the VO2 max we may have a vasoconstriction ( easy to see with MOXY) or a vasodilatation ( easy to see with MOXY.). In both cases we either increase the right or the left ventricular workload and as such a higher demand of O2 for the cardiac system. The reduction in preload will be compensated with an increase (If possible ) of HR . The increase in HR will stimulate an increase in RF and as such depending on the respiratory limitation a decrease in TV if limiting or and increase in VE if compensation.
In both cases it will demand more O2 for the respiratory system as well. The additional O2 use from cardiac and respiratory ( delivery systems ) will reduce the O2 delivery or supply to the working muscles ( easy to see with MOXY) and as such we will see a drop in performance, but a maintained of the VO2 max as it was just a shift from who may need O2 now.
This VO2 is, as so often mentioned, the sum for the total need of O2 from the “ full team”. It does not tell us at all, who uses how much at all or whether we shift theO2 use from one system to an other system due to change in limitation and delivery.
See idea of our team approach versus VO2 approach
What we will see next in studies is the fact, that in some cases the suggestion in Billat’s study is not true or not working.
a) if the muscular system is the limitation, than we see the shift of O2 use from a max reached in the muscle and a drop in performance due to muscle limitation so lower O2 use from the muscle but higher O2 use from compensatory systems like heart and respiration. So we can maintain VO2 despite a drop in performance.
2. If a vital system is the limitation than we will see not a maintaining of VO2 levels but a drop in Performance including a drop in VO2.
The main reason why we do not see that so often is, that we have vital systems limitations more often in super good trained athletes as they create an incredible muscular system with an incredible high ability to convert and try to `steel ``O2 and suddenly the delivery systems like cardiac and respiration are limiters.
Again the drift is due to shift of O2 demand to compensate for limitations. The increase in Body temperature for example will increase HR due to a drop in preload and as such a higher demand of O2 for the cardiac system so when working on a limit in performance the less O2 for actual muscle performance will drop and as such performance will drop .
A change in energy substrate availability like a lower glucose situation will shift performance ( drop and increase the O2 needed to keep delivery systems happy.
See picture form a study on heat from Australia and a study form our own lab on glucose levels. See PP
Now one last interesting part of this study.
They somehow seem to be able to get the Cardiac out put out of more than the classical idea :
CO = HR x SV
See in their study. The results.
Look at S 1 HR 161 x SV 94 = CO 15.1 True ??
Now look at S 3 193 X 179 = 34. 6 True ???
Now look at S 6 195 X 126 = 24. 5 but result really is 28.3 ???
Or the mean value is HR 184 x SV 137 = 25.2 but they have 15.1 L CO ??
Or S 8 191 X 189 our result 36.099 The studies result 30.1 L CO ??? No I do not argue they are wrong they are just different from what we used to think about CO = HR x SV ?
As this study is accepted by peer group review we have to learn how we now look and calculate CO. So any suggestion why the CO differs is welcome.