What is the limiting factor for aerobic performance in trained athletes? - Page 4

this has kind of been my thinking too... oxygen delivery is limiting because it sets hard limits to what the individual is working with.. i call the other aspects difrerentiating since they define how much of that potential you take advantage of. so it is quite possible that an individual can have great potential and have lower performance if, for example aspects of their cellular metabolism are not as addpated as another individual with lower overall potential. the is just no way to get around it those O2 define how much energy and therefor work you can produce.

..but then in keeping an open mind... i started thinking and had some questions... not hijacking the thread... all relevant to the subject at hand....

- is maximal oxygen consumption neccesarily directly corelated with sustainable oxygen consumption? not sure... probably someone with good stustainble power has a good a VO2max... but i'm not sure the reverse would necessarily have to be true.
- in the case of EPO and blood doping (and i brought these up)... is an increase in concentration of O2 per mL of blood at constant rate of flow equivalent to a change in the rate of the flow at constant concentration? not sure. O2 exchange rates might be different because of the increase of concentration of red blood cells... this might not be the case when just increase the rate of the flow... anedotally there would seem to be advantages in leaving the rate alone and increasing the concentration of RBC and as a result concentration of O2?
- at stustainable power are the muscles in an oxygen starved state? if not then O2 is in abundance or at least in adequate quantities and in the normal case O2 delivery would not limiting of sustainable power...?

just throwing some stuff out there to muddy the waters a bit more...

FWIW ... standing vs. seated ...

http://www.thesportjournal.org/2007J...o3/02bosak.asp

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rmur

I saw that article too, but then wondered if that means we're faster while standing. Does that follow? Or does the higher VO2max simply come from bringing more muscle groups into play or something? I'm puzzled.

higher VO2max comes because you are using more muscles groups and makes it possible to use up more O2 per unit time... can only squeeze so much blood through blood vessels to your legs but when you start using your arms, back and more/different muslces in your legs you are able to use up more O2 per unit time since these muscles are not supplied by the same blood vessels... doesn't mean you'll go faster, unless those new muscles are utilized in propelling the bike forward in some kind of meaninful way... which for most people they are not as a good portion of that O2 gets used just to fight against gravity an hold up your weight.

Plus, the difference in that article was quite small (2-3% in VO2max). My difference is more like 10-15% in actual power at the hub.

I may be totally missing it here but they were testing with the exact same cadence of 60 rpm. Are you using the same cadence? I would expect that to make a bigger difference when you are using different cadence.

I am not an expert, and I am sure that oxygen delivery is one of the most important things. However, just googling around, there seems to be some evidence that it may not the only limiting factor. For example, I found some studies that show that when oxygen supply goes up, VO2max goes up but not nearly as much. That is, oxygen uptake goes down, suggesting that the body can't make much use of the additional oxygen. On the other hand, I'm not sure if the long term effect of higher oxygen delivery has been studied -- it could be that the body would quickly adapt to make use of the extra oxygen.

I'm also curious how big the variance in FTP is among athletes with the same VO2max. Does anyone know? People vary by about a factor of 2 in VO2max. How much variation is there in FTP conditional on VO2max? Urkiola suggests that this might also be fairly large.

(Edited) I get what you're saying now. Yes, I use different cadences, which should lead to a bigger difference because both cadences are optimal.

I would agree. Another indicator would be that the mitochondria will increase energy production beyond what the available oxygen will support using alternate chemical processes which are less dependent upon oxygen. This is the case in even untrained individuals.

I don't think that necessarily means that stroke volume is the limiting factor, however. Insufficient capillarization around the working tissues could limit oxygen delivery where it counts, or oxygen and/or waste product transport across the cell membranes could also limit what the cells are capable of doing.

That's heavily dependent upon training. Are you suggesting that we make a meaningful comparison between the FTP of highly trained vs. lesser trained athletes? Not sure what that would prove, but I would agree that the potential for variation would be large.

Actually, I'm more interested in the variation among trained athletes here --variation in FTP conditional on VO2max. (Though now that you mention it I'm actually curious about both.)

Okay, but when the results are conditional on the extent/effectiveness of training, where do you draw the line? IOW, when you're not controlling for the expected variations, what conclusions would you expect to be able to draw from the results.

For example, rider 1 has an FTP that is 72% of pVO2max and rider 2 has an FTP that is 80% of pVO2max. That's neat and all, but does it tell us anything except that something about them or their training is different?

just going back to your original question of sustainable power seated vs. standing, as I think Alex perhaps jokingly mentioned: is your saddle too low?

I wonder if general if your bike position is simply not dialed-in very well. Saddle too low, front-end too low, too far forward .... etc so when you stand you're freeing up muscles from a 'non-optimized' position?

You're not climbing in the drops are you? Or on aerobars?

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rmur

My saddle height is perfect (I think anyway). One mm higher and my hips would rock and I would get too much leg extension (which gives me a bit of light ITBS -- I've tried it). Most fitters will say that my saddle is higher than average. As for front end, I keep the bars pretty low, but I can do almost the same power in the drops (seated) as I can sitting up, so that's not it either. (On the trainer I've tried sitting straight up even but that makes very little difference.) The one thing I haven't tried which I think might work is bringing my saddle much further forward, but this would be a pretty non-standard position. I'm pretty satisfied that having 10% higher standing power is my lot in life. I was just curious why it was happening (and if maybe someday I could train it out).

It would tell us something about how important VO2max is in determining FTP.