Lactic acid is a friend

Callistus Valerius said:

Article says Lactic acid is burned as a fuel, and that the heart loves
it. Reminds me of when I was in football, and we would complain about our
muscles, etc, and the coach said we were just lazy. Then I got into
cycling, and a whole array of excuses for not performing were the lexicon.
Lactic acid buildup, was one of them. Maybe my old football coach was right
after all.

http://www.sciencedaily.com/releases/2006/04/060420235214.htm

(If I've got what I just learned recently straight...) Although this
misunderstanding has been debunked for decades, exercise metabolism is
still a fairly young field. Things are changing.

Lactic acid IS a fuel. But the waste product of the metabolic process,
lactate, is not, and is thought to be the cause of the burn and weakness.

--
Lynn Wallace http://www.xmission.com/~lawall
I have nothing but contempt and anger for those who betray the
trust by exposing the name of our sources. They are, in my view,
the most insidious of traitors."
George H.W. Bush, April 16, 1999,

Raptor said:

Lactic acid IS a fuel. But the waste product of the metabolic process,
lactate, is not, and is thought to be the cause of the burn and weakness.

Err, lactate IS lactic acid, minus a proton.

Stay away from science.

"Kyle Legate" <[email hidden]> a écrit dans le message de news:
[email hidden]...
| Raptor wrote:
| >
| > Lactic acid IS a fuel. But the waste product of the metabolic process,
| > lactate, is not, and is thought to be the cause of the burn and
weakness.
| >
|
| Err, lactate IS lactic acid, minus a proton.
|
| Stay away from science.

Good suggestion. When someone doesn't know something, the last thing they
need is to take a discipline rigourous approach to increasing their
knowledge and understanding.

If faith based reasoning is good enough for the CIC, it's good enough for
the rest of us.

Quoted message said:

What Dr. Brooks is arguing in his body of work is that the tissues can
further oxidatively metabolize lactate to generate energy. Meaning that
Lance et al. are not only getting rid of the "burn" faster than me,
but they are also using it to produce additional energy. Seems unfair.

I'll add my 2 cents (and I'm not an exercise physiologist, and
certainly not a biochemist).

I think what you wrote is fine, but as I understand it lactic acid
isn't produced because there is a lack of oxygen, per se. It's
produced because the glycolytic rate of pyruvate production in the
muscle fiber outstrips it's ability to oxidize it, the "overflow"
pyruvate is then converted to lactic acid.

Brooks has been central in changing the view of lactic acid from an
unfortunate end product of glycolysis to the means by which the body is
able to transfer this high energy potential to other areas of the body
so that it is not wasted. So we know the lactic acid dumped in the
blood can be taken up by the liver and other muscle fibers (i.e. ones
with higher oxidative capacities or one's not working hard at the
moment) and reconverted to glycogen, or burned directly for fuel by the
heart.

However, I don't believe it's been definitely shown that muscle can
directly oxidize lactic acid like the heart can. Brooks might think it
has, but last time I checked they was still considerable debate over
the issue. As I understand it, the debate centers around locating the
transporters to get the lactic acid into the mitochondria. These exist
in the heart, Brooks thinks he's found them in skeletal muscles, others
have not been able to find them...

Raptor said:

Callistus Valerius said:

Article says Lactic acid is burned as a fuel, and that the heart loves
it. Reminds me of when I was in football, and we would complain about our
muscles, etc, and the coach said we were just lazy. Then I got into
cycling, and a whole array of excuses for not performing were the lexicon.
Lactic acid buildup, was one of them. Maybe my old football coach was right
after all.

http://www.sciencedaily.com/releases/2006/04/060420235214.htm

(If I've got what I just learned recently straight...) Although this
misunderstanding has been debunked for decades, exercise metabolism is
still a fairly young field. Things are changing.

Lactic acid IS a fuel. But the waste product of the metabolic process,
lactate, is not, and is thought to be the cause of the burn and weakness.

There is a thread on rec.skiing.nordic about the same topic that has
some informative summaries of what may be going on:

http://groups.google.com/group/rec.skiing.nordic/tree/browse_frm/thread/fab93e2ff22b42d4/0e0168ada851da34

Joseph

<[email hidden]> a écrit dans le message de news:
[email hidden]...
I'm going to have to agree with Kyle on this one. Disseminating faulty
information as fact does no one good.

Nor does writing "Stay away from science."

True. The ideas that Dr. Brooks is putting forth are very far from
being
any sort of established and excepted scientific theory. I was just
trying
to summarize his main argument, and was *not* assign attempting to
assess its truthfulness. I leave that to the experts debating in the
primary literature.

And yes, your are correct that lactate is not a direct result of
absence
of oxygen, but is more a consequence of the relative rates of pyruvate
oxidation (aerobic metabolism) and reduction (lactate formation).
However, the oxygen concentration argument is frequently useful when
comparing aerobic vs. anaerobic mechanisms. I should have been
more clear on that point. Having said that, the relative rate of
pyruvate oxiation and lactate formation is invariably affected by
oxygen
concentration --- compare sprinting flat out at sea level to sprinting
at
elevation.

Quoted message said:

Quoted message said:

What Dr. Brooks is arguing in his body of work is that the tissues can
further oxidatively metabolize lactate to generate energy. Meaning that
Lance et al. are not only getting rid of the "burn" faster than me,
but they are also using it to produce additional energy. Seems unfair.

I'll add my 2 cents (and I'm not an exercise physiologist, and
certainly not a biochemist).

I think what you wrote is fine, but as I understand it lactic acid
isn't produced because there is a lack of oxygen, per se. It's
produced because the glycolytic rate of pyruvate production in the
muscle fiber outstrips it's ability to oxidize it, the "overflow"
pyruvate is then converted to lactic acid.

Brooks has been central in changing the view of lactic acid from an
unfortunate end product of glycolysis to the means by which the body is
able to transfer this high energy potential to other areas of the body
so that it is not wasted. So we know the lactic acid dumped in the
blood can be taken up by the liver and other muscle fibers (i.e. ones
with higher oxidative capacities or one's not working hard at the
moment) and reconverted to glycogen, or burned directly for fuel by the
heart.

However, I don't believe it's been definitely shown that muscle can
directly oxidize lactic acid like the heart can. Brooks might think it
has, but last time I checked they was still considerable debate over
the issue. As I understand it, the debate centers around locating the
transporters to get the lactic acid into the mitochondria. These exist
in the heart, Brooks thinks he's found them in skeletal muscles, others
have not been able to find them...

trg said:

<[email hidden]> a écrit dans le message de news:
[email hidden]...
I'm going to have to agree with Kyle on this one. Disseminating faulty
information as fact does no one good.

Nor does writing "Stay away from science."

I meant stay away from dispensing science without knowing for certain
whether you're right.

"Kyle Legate" <[email hidden]> a écrit dans le message de news:
[email hidden]...
| trg wrote:
| > <[email hidden]> a écrit dans le message de news:
| > [email hidden]...
| > I'm going to have to agree with Kyle on this one. Disseminating faulty
| > information as fact does no one good.
| >
| > Nor does writing "Stay away from science."
| >
| >
| I meant stay away from dispensing science without knowing for certain
| whether you're right.

Oh, sorry. I mistook your meaning. Nevermind..

Kyle Legate said:

Raptor said:

Lactic acid IS a fuel. But the waste product of the metabolic process,
lactate, is not, and is thought to be the cause of the burn and weakness.

Err, lactate IS lactic acid, minus a proton.

Stay away from science.

I know that, more or less. What I merely suspect (and could confirm by
poring through a book I have, probably) is that the metabolic process
strips the proton, leaving lactate, which is the problem.

If I had a degree in exercise physiology or a related field, I'd be
embarrassed by my lack of knowledge.

--
Lynn Wallace http://www.xmission.com/~lawall
I have nothing but contempt and anger for those who betray the
trust by exposing the name of our sources. They are, in my view,
the most insidious of traitors."
George H.W. Bush, April 16, 1999,

Quoted message said:

I'm going to have to agree with Kyle on this one. Disseminating faulty
information as fact does no one good. Having said that, I'm going to
set myself up for a fall by providing a brief overview of the press
release below.

See, that's why I craftily inserted a disclaimer in my putatively
factual contribution. Having been a follower of rbr for decades, I know
that there's a lot of bright people here. I have no problem whatsoever
saying, "I stand corrected."

--
Lynn Wallace http://www.xmission.com/~lawall
I have nothing but contempt and anger for those who betray the
trust by exposing the name of our sources. They are, in my view,
the most insidious of traitors."
George H.W. Bush, April 16, 1999,

Kyle Legate said:

trg said:

<[email hidden]> a écrit dans le message de news:
[email hidden]...
I'm going to have to agree with Kyle on this one. Disseminating faulty
information as fact does no one good.

Nor does writing "Stay away from science."

I meant stay away from dispensing science without knowing for certain
whether you're right.

So what does, "If I've got what I just learned recently straight..."
mean to you?

--
Lynn Wallace http://www.xmission.com/~lawall
I have nothing but contempt and anger for those who betray the
trust by exposing the name of our sources. They are, in my view,
the most insidious of traitors."
George H.W. Bush, April 16, 1999,

Raptor said:

Kyle Legate said:

trg said:

<[email hidden]> a écrit dans le message de news:
[email hidden]...
I'm going to have to agree with Kyle on this one. Disseminating faulty
information as fact does no one good.

Nor does writing "Stay away from science."

I meant stay away from dispensing science without knowing for certain
whether you're right.

So what does, "If I've got what I just learned recently straight..."
mean to you?

Nothing.

In article <[email hidden]>,

Raptor said:

Kyle Legate said:

Raptor said:

Lactic acid IS a fuel. But the waste product of the metabolic process,
lactate, is not, and is thought to be the cause of the burn and weakness.

Err, lactate IS lactic acid, minus a proton.

Stay away from science.

I know that, more or less. What I merely suspect (and could confirm by
poring through a book I have, probably) is that the metabolic process
strips the proton, leaving lactate, which is the problem.

Not even wrong. The books have not caught up.

Tom posted a URL to this excellent survey article:
<http://ajpregu.physiology.org/cgi/content/full/287/3/R502>

H+ comes from glucose and glycogen metabolism used to
generate ATP, and from ATP hydrolysis outside the
mitochondria. The H+ is moved into the mitochondria where
it can `function as a substrate for oxidative
phosphorylation.' At high effort the capacity for the
mitochondria to take up H+ is overloaded and H+ starts to
build up. Various buffering and transport mechanisms act
to reduce acidosis; but acidosis rises as high effort is
maintained until total muscle fatigue results. One of the
buffering mechanisms is lactate + H+. Also lactate + H+ is
transported out of the cell into the blood stream. Hence
the misapprehension that production of lactic acid is the
_cause_ of acidosis. In fact no chemical reaction in the
cell _produces_ lactic acid. Lactate is produced, and H+
is produced.

--
Michael Press