"Andy Coggan" <
[email protected]> wrote in message news:<
> > > It sets the upper limit to aerobic energy production, yes (and
> obviously).
> > > However, it isn't the only determinant of endurance exercise
> performance, as
> > > I have explained previously.
> >
> > It only sets the upper limit at that point in time. It doesn't mean VO2 max cannot be increased.
> > It is a number. What is the basis of that number? is it cardiac? pulmonary? or skeletal muscular
> > limits that set VO2 max? Maybe we should be debating that question. Which do you believe to be
> > the limiter that determines VO2 max?
>
> Personally, I'm more of a subscriber to what's sometimes referred to as metabolic control theory,
> or distributed control - this helps you get away from thinking that one thing, and only one thing,
> limits any particular process. However, if you look at the overall chain of events involved in O2
> transport during maximal exercise, there's absolutely no question whatsoever that convective O2
> delivery - which is determined by cardiac output and arterial O2 content - is the primary
> determinant of VO2max. By comparison, the ability of muscle to accept blood flow and to take up
> and utilize O2 is far, far greater, whereas the lungs, although lacking the same degree of safety
> margin (if you will), are also somewhat "overbuilt" for exercise (in most cases).
The amount of convective O2 delivery at maximum exercise IS VO2 max. I guess that in a fashion could
be considered to be the "primary" determinant in VO2 max but if you were my student I wouldn't
accept that answer as showing an adequate understanding of the physiology, you have just
regurgitated the definition. What again is the limiter that prevents us from further increasing our
VO2 max when we are doing these tests? I presume you have excluded the lungs from your answer above
(I would agree) so now we are down to the heart or the periphery (local tissue blood dynamics). Two
choices in my mind, unless you can think of a third.
>
> > > > In another post, which I just answered, you stated that my claim was I increased power 40%
> > > > and that would mean you had to increase your VO2 max 40%, so my claims are snake oil. so, in
> > > > my mind, that is what you believe. You apparently do not think it possible to improve
> > > > efficiency to get more power to the wheel from the same engine. What else are we supposed to
> > > > think based upon that (and other) posts.
> > >
> > > I never said that efficiency was fixed - it just isn't possible to
> improve
> > > efficiency by 40%. This is true because the way that efficiency is
> typically
> > > expressed (i.e., useful work accomplished/energy released) fails to take into account the
> > > obligatory energy "loss" that occurs during metabolism
> (vs.
> > > burning foodstuffs in an indirect calorimeter). If you do take that into account (and the fact
> > > that efficiency as calculated based on O2 uptake
> by
> > > the leg is higher than efficiency as calculated based on O2 uptake by
> the
> > > whole body), you realize that our muscles are actually already markedly efficient, meaning
> > > that such a large increase is simply impossible. Even
> if
> > > it were, however, I don't believe that trying to "pedal circles" would improve efficiency -
> > > this has been a red herring in cycling ever since bicycles were invented, as anybody who
> > > *really* understands the
> biomechanics
> > > and physiology of cycling realizes.
> >
> > Well, if the typical cyclist pedals at an efficiency of 20% and the effiiciency of the
> > conversion of chemical energy into work by the muscles is slightly more than 40% then it is in
> > fact POSSIBLE to improve efficiency by more than 40% as a 40% improvement would only take the
> > 20% efficient body to a overall efficiency of 28% (it would take the 26% efficeint cyclist
> > (about the highest ever measured) to 36%, less probable but possible). Even so, I only claim the
> > typical rider will receive 40% increase in power so some of this may come from increase in VO2
> > uptake from use of new muscles, so all of this increase doesn't need to come from improved
> > efficiency.
>
> Boy, you're a slippery one, Frank! First you claim a 40% increase in power in absolute terms, now
> you state that it is 40% in a relative sense (first sentence above), then finally you go back to
> claiming it is a 40% increase in absolute terms - make up your mind, will you?
I am slippery. It is all that snake oil. I am confused by your confusion. I am simply trying to say
there are many potential mechanisms for improving power to the wheel. 40% is approximately what most
people see.
>
> I guess it's time for a little biochemisty/physiology/math lesson for ol' Frankie...
My pencil is out ...
>
> Using myself as an example: mashing on my pedals at ~80 rpm, I can sustain 300 W for ~1 h, a power
> output that requires (ignoring any VO2 drift) a VO2 of 3.8 L/min, or ~85% of my VO2max. My gross
> efficiency at this intensity is 22.5%. However, gross efficiency reflects the efficiency of the
> body as a whole, not that of the working leg muscles. The latter can be estimated knowing that the
> % of whole-body O2 uptake by the legs during cycling is comparable to the percentage of VO2max -
> IOW, at 85% of my VO2max about 85% of whole body O2 uptake is by my legs, i.e., my leg O2 uptake
> at 300 W = 3.8
> L/min x 0.85 = 3.2 L/min. In turn, that means my leg muscles are working with an efficiency of
> 26.8%. At such a high relative intensity, carbohydrate will be the primary (if not the
> exclusive) fuel. Regardless of whether the reaction proceeds in vivo or in a bomb calorimeter,
> the complete oxidation of 1 mol of glucose using 6 mol of O2 yields 6 mol of CO2 and 6 mol of
> H2O, and most importantly liberates 673 kcal of energy. Of this 673 kcal, however, only 450 kcal
> are "trapped" in the form of ATP (36 mol with a delta G zero in vivo of -12.5 kcal/mol). IOW,
> aerobic metabolism of glucose is only 450/673 = 67% efficient in the first place. Thus, the
> efficiency of my muscles in converting the energy that is trapped as ATP into useful work is
> actually already 26.8/0.67 = 40%! This rivals or even exeeds the efficiency of mechanical
> devices, e.g., electric motors. Given this, and the fact that the 1st law of thermodynamics
> means that there *must* be an increase in enthalpy of the system as a whole when ATP is broken
> down to drive muscle contraction, the notion that you can achieve a 40% increase in power simply
> by "pedaling circles" is ludicrous at best. Furthermore, since I'm already capable of sustaining
> exercise very close to my VO2max for many tens of minutes at a time, there is little if any
> "room" for increasing power output simply by operating at a higher percentage of VO2max. Ergo,
> the only way to achieve the phenomenal increases in power that you claim would be by increasing
> VO2max itself...but since it takes but a small fraction of total body muscle to be contracting
> to drive cardiac output to its limits, there's no reason to believe that attempting to bring a
> few small accessory muscles into play would be of any benefit there, either. (If there were,
> then you'd expect that arm+leg trained athletes, e.g., X-C skiers to have higher VO2max values
> than e.g., middle distance runners - but in fact, they don't.)
So, let me get this straight. You are already pretty good so it is not conceivable that you could
improve much more, let alone an increase of 40%. Especially because you're already at 40% (40% of
the theoretical maximum). Wow, that is pretty good. I am impressed.
However, you just got a few things wrong. I claim the typical user will see a 40% increase in POWER,
not efficiency. I believe such improvements in efficiency are probably possible but I don't know
that and don't claim it. so, I don't claim all of the gains are due to improvements in efficiency. I
think most of the early gains are however. But, other improvements come from recruiting more muscle
mass, eventually increasing VO2 max. But, let us presume I am claiming a 40% improvment in
efficiency, even for an elite athlete such as yourself. All I am saying is a 40% increase in your
current muscular efficiency of 26% gives an increase of about 10% or will get you to 36% musclular
efficiency, or slight more than half the theoretical maximum. That may or may not be possible to
acutally achieve but it certainly is not theoretically impossible. I know this, it is not possible
if you don't try. People who use the cranks typically report gains suggestive of such gains in them.
People who don't use them, don't.
>
> > So, it is possible this all comes from efficiency improvement. You just don't think it probable.
> > Am I right?
>
> Correct.
>
> > If the 40% improvement in power in the typical rider (or say smaller improvements in the elite
> > rider such as the 28% seen by Phil Holman) are shown to be true. Where do you think these
> > improvements are coming from? Or, are you still saying it is not possible?
>
> Since few endurance athletes devote significant attention to developing their neuromuscular
> power/anaerobic capacity, improvements such as Phil's can readily be explained by a period of
> training focussing on this ability. For example, I have power data on an elite track cyclist
> showing a 25% increase 5 s and 1 min power in just 2 months, simply as a result of changing the
> emphasis of their training. (I expect to make similar gains myself during my specific prep for the
> 3k pursuit at master nationals this year, which, since I've already gone as fast as Phil for 2k
> during a 3k event w/o any specific training, should enable me to blow away the time he always
> likes to brag about...but that's a different story.)
Wow. I am impressed. Just one question. How often can people improve "simply as a result of changing
the emphasis of their training"? Could someone do this every 3 months or so to get to the TDF in 3
or 4 years. How about Jan? could he do this this spring and kick Lances butt this summer? I take it
that you don't see those who take up PowerCranks as changing the emphasis of their training, at
least in anyway positive. Based upon your explanations I am now no longer looking forward to seeing
how Erin Mirabella performs this season on the track as she has changed the emphasis of her training
to include PowerCranks. Probably won't even get invited to the trials. Poor thing. Maybe you should
write and warn her she has been taken in by a snake oil salesman to help her save her season.
>
> > > > > > If you continue to insist upon this mechanism, how do you explain these differences?
> > > > >
> > > > > What differences do you mean? Between sports? They're really aren't
> any,
> > > > > once you consider how VO2max scales with body mass. Between
> individuals?
> > > > > Simple: while VO2max sets the upper limits to aerobic energy
> production, the
> > > > > fraction of VO2max that can be utilized for given period of time
> (determined
> > > > > by "metabolic fitness", measured via LT) is also an important factor
> (as is
> > > > > efficiency/economy of movement - which for cycling seems to be most
> closely
> > > > > related to biochemical, not biomechanical, factors). Consequently,
> having an
> > > > > adequately high VO2max is a necessary but not a sufficient condition
> for
> > > > > elite endurance performance.
> > > >
> > > > It makes no sense to me to say VO2 max is limiting and then scale it to body weight. If it
> > > > should be scaled to anything it should be lung capacity
> > >
> > > And why, pray tell, is that? Except in special cases, the lungs aren't limiting to VO2max,
> > > i.e., most (not all) people have no problem
> maintaining
> > > arterial O2 saturation even during maximal exercise.
> >
> > And that is why VO2 max is not limiting to aerobic exercise? Thanks for the argument. If
> > arterial oxygenation is maintained during maximal exercise, why do you presume to claim that VO2
> > max is limiting?
> > >
> > > > , something that doesn't change with training and hardly changes with weight. Further, since
> > > > VO2 max can increase with training I don't believe it to be limiting.
> > >
> > > Huh? That's as dumb as sauing that because I can hot-rod my car to make
> it
> > > go faster, the amount of horsepower that it makes in its present state doesn't limit its
> > > speed.
> >
> > that is not dumb, it is true.
>
> No, it is just plain dumb.
Then dumb it is!
>
> > Let us get back to what the limiting organ ireally is. i will accept your argument that VO2 max
> > limits aerobic exercise performance. What limits VO2 max. The heart or the periphery or
> > something else?
>
> Once again, primarily the heart.
Why do you say that? What specifically happens that limits further increases in the hearts ability
to pump blood? Does the heart become ischemic (for those of you who are still around and now
familiar with the jargon, that means not enough oxygen) and can't generate any more energy? Why
doesn't the athlete experience chest pain if the heart can do no more? Give me a physiological
mechanism for this limitation.
>
> > > > > > How do you explain incremental improvements in VO2 max with incremental additional
> > > > > > training?
> > > > >
> > > > > By increases in stroke volume and/or a-vO2 difference (primarily the
> former,
> > > > > at least when talking large changes in VO2max....a-vO2 difference
> can only
> > > > > increase by ~10%, since during maximal exercise there isn't much O2 remaining in mixed
> > > > > venous blood even in an untrained person).
> > > >
> > > > Actually, it is mostly a combination of increases in stroke volume and increased heart rate.
> > >
> > > Sorry, but maximal heart rate goes down, not up, with training. Hence,
> all
> > > of the increase in maximal cardiac output - and typically at least 50%
> of
> > > the increase in VO2max - is due to the increase in stroke volume.
> >
> > Possibly, but age goes up with training which is associated with lowered maximum heart rates.
> > the top aerobic athletes are not 20 years old but more likely 35. That explains the maximum HR
> > connundrum.
> > >
> > > > In regards to the a-vO2 difference, even though I am not familiar with this data I will
> > > > boldly say this, phooey! As long as the athlete is aerobic mixed venous blood will remain at
> > > > a pO2 of about 40 (75% saturated). When this starts to drop will be close to lactate
> > > > threshold and will be close to VO2 max.
> > >
> > > Frank, once again you reveal your ignorance about the physiology of exercise: the O2 content
> > > of mixed venous blood drops rapidly as a result
> of
> > > the transition from rest to low intensity exercise, then declines much
> more
> > > gradually thereafter. Since arterial O2 content is essentially constant (perhap rising
> > > slightly up to moderately intense exercise, then
> declining
> > > back to resting or perhaps slightly below resting as VO2max is
> approached),
> > > the whole-body a-vO2 difference increases basically mirrors the change
> in
> > > mixed venous O2 content. There is no abrupt transition in mixed venous
> O2
> > > content around LT or VO2max as you claim. Furthermore, although there
> isn't
> > > much O2 left in venous blood (esp. that draining exercising muscle)
> during
> > > exercise in the untrained state, there is some - and one of the effects
> of
> > > training is enhance O2 extraction both across the muscle and for the
> body as
> > > a whole. This widening of the a-vO2 difference with training typically accounts for ~50% of
> > > the icnrease in VO2max when individuals undergo a moderate period of endurance training (e.g.,
> > > a few months) and achieve a moderate increase in VO2max (e.g., ~20%). Even that conclusion,
> > > though,
> is
> > > really a synthesis of the literature, as in fact some studies find that
> the
> > > increase in a-vO2 differences accounts for *ALL* of the increase in
> VO2max
> > > with training (and others find that it doesn't change at all, probably because of the
> > > difficulty of measuring or calculating a-vO2 differences
> with
> > > great accuracy during maximal exercise).
> >
> > mixed venous O2 saturation simply represents the average of all the blood returning to the
> > heart.
>
> Correct, but training increases a-vO2 difference even when measured across exercising muscle
> itself. IOW, increased shunting doesn't explain the increase in whole-body a-vO2 difference (and
> hence VO2max) with training (although decreased shunting may contribute to the age-related decline
> in VO2max, approximately one-third of which is due to reduced O2 extraction).
>
> > This includes blood returning from the skin and gut where O2 levels may be high and muscle where
> > it will be lower. It will be normal for mixed venous concentration to drop during intense
> > exercise because a greater percentage of the blood is coming from high extraction organs. This
> > drop will be less in hot weather where a higher percentage of the blood goes to the skin for
> > cooling.
>
> More non-sequitors.
>
> > It doesn't affect the basic tenets of my arguments.
>
> Except that it reveals your ignorance with regards to many things of which you speak. Given this,
> is it any surprise that educated people tend to dismiss you as a charlatan, and your invention as
> a gimmick?
In the beginning I was surprised. i am no longer. Now I am embarking off on a quest to toconvince
the running gurus. Why am I expecting more of the same? At least I am comforted by the fact that
there is not ignorance reavealed in ALL the things I speak. whew!
>
> > > > Where does the increase in stroke volume come from? Increased filling pressure I say.
> > >
> > > That's part of it, but only part: there's also an increase in intrinsic myocardial
> > > contractility and rate of relaxation, as well as changes in sensitivity to adrenergic
> > > stimulation - see, for example:
> > >
> > >
>
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1537731&dopt=A-
> bstract
> > >
> > > > Where does the increased filling pressure come from? Increased venous return I say. Where
> > > > does the increased venous return come from? Increased blood flow through the muscle due to
> > > > local autoregulation I say. So, cardiac output responds to venous return which is determined
> > > > by local conditions. When the local muscle cannot pass any more blood, cardiac output (and
> > > > hence VO2 uptake) ceases to increase and we soon reach VO2 max (as there is a little further
> > > > uptake due to increased extraction. If the muscle could pass more blood then cardiac output
> > > > would increase and VO2 max would also increase. It is that simple.
> > >
> > > So by your understanding, alpha blockade using e.g., phentolamine would result in an increase
> > > in VO2max. Why don't you try that and report back
> to
> > > us, Frank?
> >
> > Alpha blockade would have no significant effect on VO2 max i suspect.
>
> You apparently claim that "local conditions" (vascular conductance of muscle) are the sole
> determinant of venous return, which in turn is the sole determinant of stroke volume and hence
> cardiac output and VO2max. At least, that's what I take you to mean when you say "It is that
> simple".
there can be other determiinants but they are generally short term.
>If this were correct, then alpha blockade, which would prevent vasoconstriction (which occurs even
>in exercising muscle, at least if more than a small fraction of total muscle is engaged in the
>activity), would, by your theory, increase venous return, stroke volume, cardiac output, and
>VO2max. In fact, what it *really* does is make high intensity exercise impossible (such that VO2max
>cannot be reached), since you can no longer maintain adequate blood pressure.
That is because you are opening vascular beds in tissue that are not utilizing oxygen, and creating
a peripheral AV shunt and diverting blood from the muscles that need it. The heart only has a small
excess capacity. It is not normally limiting except when you do something stupid like that. So, of
course such a stupid stunt adversely affects performance. Duh!
>My comment was therefore meant primarily as a joke, but the mere fact that you failed to recognize
>this possiblity once again illustrates how little you actually know about exercise physiology, much
>less physiology in general.
Well you fooled me. I guess that must seem pretty easy to do with someone with such a miniscule
knowledge in this area. i will try harder in the future.
Frank
