Definiton of Aerobic and Anaerobic, lets get up to date here.

Come on Alan, you talk physiology all the time. More than 90% of your posts concern the physiology of running.

All I am trying to do here is sort out the old science which has been refuted, by presenting the work of the best people in their field of research. I will be able to simplify it later.

So you know information I don't know, I know info you don't know. What is stopping you from giving that info here. Are you afraid that I might disagree?

Okay, my understanding is that brief bursts of physical effort (eg 60 meter sprint) draw almost exclusively on anaerobic energy production -- although obviously there is also aerobic production going on at the same time.

In the first few strides of a a 5K this is the prime energy source.

Soon after that the vastly more efficient aerobic system predominates. Small amounts of energy are probably still being produced anaerobically.

Now we get to the end of a 5K. Can someone explain what terms make the most sense to describe what energy systems are at work in the last 1000 meters and the final 100 meters?

Forget "lactic acid" -- I'm convinced that "lactate" is the more appropriate term.

Still ... at the end of the race is there indeed a shift back toward more energy being produced by anaerobic systems, as there was at the beginning of the run?

If this is correct, why can't this properly be termed "going anaerobic"?

After all, no one refers to a runner "going entirely anaerobic with no aerobic energy production whatsoever."

The more I think about this, the more I'm convinced that "going anaerobic" is an appropriate term.

Look at that final 100 meters in the scenario above. The runner sprints for the tape. The effort exceeds the aerobic pathway, so it's supplemented by anaerobic energy production (ATP, ADP, all that jazz).

So the runner "went anaerobic" as he sprinted for the line -- right???

How about this:

In the presence of sufficient oxygen, glucose is converted to pyruvate (aerobic glycolysis), which results in ATP (i.e., energy). In the absence of sufficient oxygen, glucose is converted to lactate (the salt or ester of lactic acid - anaerobic glycolysis), which results in less ATP.

Generally speaking, when the body's demands for oxygen exceed its ability to acquire O2, it will rely more heavily upon anaerobic glycolysis to produce energy.

While there are always at least some amount of anaerobic glycolysis / respiration taking place, in light of the above stated, "going anaerobic" is an incredibly practical term, though not an "on-off" switch.

I believe there is another source of anaerobic ATP that runs out after about 50 meters of effort. This is why 100 meter sprinters aren't actually going "100% all out" the entire race!

I kind of agree -- I don't have a problem with "going anaerobic". That's not the same as being indifferent about "lactic acidosis" or "lactic acid" -- I agree these terms seem incorrect.

But why are we talking about what happens in a 5K race, or any race? I think it is more important to talk about anaerobic and aerobic when you are training, not racing.

"wellnow" pointed out that the ratio of aerobic/anaerobic running isn't what we were told -- the aerobic component is higher due to lactate consumption as an aerobic fuel.

However, in training, we do "fast" intervals in order to trigger "anaerobic" production of ATP, so that high volumes of lactate accumulates. Lactate accumulation by "anaerobic" production of ATP doesn't happen at easy "aerobic" pace, or "tempo" pace, but does happen with "fast" intervals. Why can't we call that "going anaerobic"? For "fast" interval training, it's not really important what the ratio of aerobic to anaerobic is -- what's important is that the demand for anaerobic ATP is high enough to produce huge quantities of lactate (presumably so we adapt to that). Calling that "aerobic", because the aerobic component might still be greater, is to emphasize the unimportant -- only adding more confusion.

The race scenario was just to clarify the point.

When discussing racing or training, we've clearly established that aerobic and anaerobic are useful terms.

Furthermore, "aerobic threshold," while not an particularly precise or scientifically well-defined term, is nonetheless a useful concept for describing training protocols.

If you want to obsess about the exact metabolic pathways at work during all phases of running you're probably better suited to research and should refrain from commenting on coaching or running.

Thanks for playing.

The aerobic system, isn't vastly more efficient. That is on of the myths I am trying to debunk. In the old literature, which is still copied into new literature, it says that anaerobic respiration is 18x less efficient than aerobic respiration.

This is wrong. If there are only 2 ATP produced and used by anaerobic respiration, for every 36 available for pyruvate or lactate oxidation(aerobic resprition), it's because that is the proportion available for each, So that is a total of 38 ATP

So where is the inneficiency?

2 ATP are used up in Glycolysis, another 2 are produced and used up anaerobically, and another 36 are available for aerobic respiration. The numbers vary depending on which reactions take place.

There is no inneficiency other than heat production, which is a metabolic inevitablity.

We humans produce a lot of heat regardless of whether we are engaged in high intensity excercise, or resting. Obviously we produce different amounts according to metabolic rate.

We also produce a lot of heat whether we are hot or cold, but the measurements of this heat loss in terms of aerobic/anaerobically derived heat production are almost impossible to measure accurately.

Your other question about going anaerobic is a good one.

Yes, at the end of a 5000m race, you pick up the pace gradually sometime in the last 1000m, then again on the last lap, and then sprint from about 200m out. The rate of anaerobically derived energy increases during each pick up for a few seconds because you are starting to wind it up, and running maybe ten secods quicker for that lap. However, the amount of anaerobically derived energy quickly starts to run out again, as it did at the start of the race, and in the last 100m the amount of aerobically derived energy increases again, until you are at your limit of effort (if you are trying to outkick the other guys) just as you cross the line.

This explains why, you feel terrible with 250m to go, and then when you kick you feel good for a few seconds (if you have a reasonable kick) and then you gradually go back to feeling terrible again as the finish line approaches and you fight the other guys and the rising fatigue.

So you don't "go anaerobic" in the last 1000m or the last lap, you use a subtle mixture of both aerobic and anaerobic, as you do throughout the race, the amount of each varying constanly, having been practising this all of your life to perfect.

I hope that helps. If you are tired from work and running, you might have to read it a few times.

To my ear "going anaerobic" sounds better than "the metabolic pathway becomes biased toward anaerobically derived energy" or some such.

So I don't see the point in correcting someone who uses the terms aerobic and anaerobic ... unless they're trying to describe something in terms of precise physiology.

Maybe we should call it "turnin on the booster rockets"?

We can do this many times in a 5000m race, and in interval training.

Anything that gives a runner more confidence about The Lactate Shuttle.

What is the lactate shuttle? Well it helps to describe what the old Lactate Threshold concept can't explain, i.e. how come them Africans is so fast?

We have been constantly told that "Lactic acid" is the demon of the distance runner.

Their is no Lactic acid.

Lactate is not an acid, and it is not your enemy, it is your freind.

Let's get up to date here.

wellnow wrote:

This is wrong. If there are only 2 ATP produced and used by anaerobic respiration, for every 36 available for pyruvate or lactate oxidation(aerobic respiration), it's because that is the proportion available for each, So that is a total of 38 ATP

So where is the inefficiency?

2 ATP are used up in Glycolysis, another 2 are produced and used up anaerobically, and another 36 are available for aerobic respiration. The numbers vary depending on which reactions take place.

I keep coming back to the time aspect, that is, the observation that blood lactate levels steadily rise throughout a 5k race. How does this not lead to the conclusion that the anaerobic process is producing its byproducts faster than they are being consumed by oxidative processes?

Your observation that there is no metabolic inefficiency (i.e. no "going anaerobic") is true if you consider the net metabolism from the beginning of the race until, say, an hour after it is over, but it doesn't appear to be the case during the race.

Blood lactate levels don't really tell you what is going on in the muscle. That is why George Brooks' lactate shuttle hypothesis is so important, because he is working to explain what is really going on.

This takes us beyond the Lactate Threshold concept, which is really just the Anaerobic Threshold concept with a different name.

Yes there is lactate accumulation during a 5000m race, but some of this lactate is stored in muscles which aren't working as hard, and slowly released during the race for aerobic fuel.

There is always lactate accumulation after any high intensity race. This is also metabolically favorable, since it helps us to recover after the race, or help us to make anothe effort if we need to. This is a survival mechanism. If we didn't have this ability to make a repeat effort, then the human race would not have survived.

The efficiency/inneficiency problem I was refering to was a misunderstanding which continues from the time when it was thought that Anaerobic Glycolysis produced a waste product; "lactic acid" which supposedly poisoned the muscles and was thus inneficient.

The textbooks have not updated this error.

B0ulderite wrote:

To my ear "going anaerobic" sounds better than "the metabolic pathway becomes biased toward anaerobically derived energy" or some such.

So I don't see the point in correcting someone who uses the terms aerobic and anaerobic ... unless they're trying to describe something in terms of precise physiology.

There is a major problem in the fact that what most people call aerobic and anaerobic is back to front, in complete contradiction of what physiologist have been writing for the past 30 or so years.

This is bound to cause confusion. We actually start a race using Anaerobic sources of energy, and then go towards more Aerobic.

So we don't "go anaerobic" ........... we "go aerobic"

even in 100m 200m 400m 800m races

"Back to Front" and "Complete Contradiction"? So are you saying that slow running is more anaerobic?

Maybe I just don't understand what people mean by "going anaerobic", such that you disagree with it.

You keep talking about where the lactate is going, but where is the lactate coming from -- aerobic running? What is the significance of comparing the ratio of aerobic to anaerobic at any given pace?

Help me fix my model:

Slow, aerobic running, doesn't produce any blood lactate accumulation.

Medium, tempo running does produce lactate accumulation, but not so much that our bodies can't handle it in realtime.

Fast running produces a high lactate accumulation, more than our bodies can deal with, triggering adaptations to deal with it better the next time. This lactate is a by-product of anaerobically derived ATP.

Why then is it a mistake to say fast running is anaerobic? Isn't that the key characteristic which separates it from slower running? I'm happy calling it anaerobic, because that's what generates so much lactate, which exceeds our bodies ability to clear it, or tolerate it. What happens aerobically is just irrelevant in discussions involving lactate accumulation. Why should we emphasize it?

From what I can tell from this hypothesis, which is widely, but not completely, accepted, the lactate buildup is not the cause of the bulk of the soreness associated with intense workouts. It is thought that the acidosis related to exercise may be totally unrelated to lactate buildup, but more with the conversion of large amounts ATP to ADP that involves the production of H+.

I think one thing wellnow is not clearly pointing out is what you are pointing out. At lower exertion, the body transports enough oxygen to the muscle to allow for breakdown of lactate/pyruvate and production of ATP, this is traditionally "running aerobically". At high exertion, oxygen delivery is not sufficient to allow for this breakdown of lactate and then, your energy production is limited by oxygen. The harder you exert yourself, a higher proportion of energy is being produced by glycolysis. This is what traditionally has been called "going anaerobic".

The unresolved question is what metabolic pathways lead to muscle soreness from acidosis. Is it tightly tied to being limited by oxygen? It seems clear, now, that it is not lactate/lactic acid that is the proximal cause.

What I mean when I say that the popular belief of going anaerobic is back to front is that we start a race using mostly anaerobically derived energy and then go to aerobically derived energy.

What happens aerobically is EXTREMEY IMPORTANT in discussions involving lactate accumulation. That is Why should we emphasize it?

EXTREMELY IMPORTANT even.

Oxygen delivery is ALWAYS sufficient during lactate production. It is another myth that lactate is produced because of low oxygen delivery.

George Brooks is the man to explain all of this in his cell to cell lactate shuttle hypothesis, which I will address soon.

Wellnow, on Lydiard-Daniels, Tinman has joined the Lydiardites in calling anyone who debates with them "Skuj". (ie now they are saying wellnow is Skuj.) Please email Tinman and set him straight. I hate to see a smart guy make a fool of himself.

Discuss.

wellnow wrote:

Oxygen delivery is ALWAYS sufficient during lactate production. It is another myth that lactate is produced because of low oxygen delivery.

If you want to explain this, you are going to have to learn to read what other people write and not make these incorrect characterizations. I said that at high levels of exertion, the production of energy (ATP) is limited by oxygen delivery because lactate oxidation (break down of lactate into ATP) is limited by oxygen delivery.

Are you saying that production of ATP is never limited by oxygen delivery?