New Lactic Acid Research - Triathlon Week

08-23-2004, 07:09 PM

from a post on another newsgroup...

Full Text : Allen and Westerblad, PHYSIOLOGY: Enhanced: Lactic Acid--The
Latest Performance-Enhancing Drug, Science 2004 305: 1112-1113
[Only registered and activated users can see links. ]

----- Original Message -----
From: "Larry Weisenthal" <runnswim@aol.comnet>
Newsgroups: rec.sport.swimming
Sent: Saturday, August 21, 2004 4:57 AM
Subject: Lactic Acid Paradigm Shift

> On NPR Friday there was an in depth science story which was of monumental
> importance to exercise physiology. Published in Science. I haven't read
it
> yet, but basically, it goes like this:
>
> Conventional thinking is that lactic acid is something bad...which
degrades
> muscle performance. Lactic acid forms when there is so much sugar
metabolism
> that the mitochondria of the cells can't handle it. Glucose is degraded
to
> pyruvate to make ATP to power the muscle contraction. The pyruvate then
enters
> the mitochondria to go into the Krebs cycle to make still more ATP. But
when
> pyruvate is produced so fast that it can't be processed by the
mitochondria, it
> gets converted to lactic acid, which is either stored in the muscle cell
or
> washed away into the blood stream. Lactic acid is a temporary storage
form of
> potential energy. Once the mitochondria have caught up, lactic acid can
be
> metabolized in the mitochondria to produce ATP to power muscles. In fact,
the
> preferred energy source for cardiac muscle is lactic acid, although all
muscles
> can "burn" it to produce ATP.
>
> But the "problem" is that lactic acid lowers the pH of the muscle cells.
> Conventional wisdom is that this is bad and that the falling pH is
responsible
> for "poisoning" muscle contraction. So this has led to all sorts of
theories
> about training improving the "buffer capacity" of muscle cells (you can
read
> about this everywhere, including in Maglischo). And it has led to all
sorts of
> nutritional supplements to imrpove buffering to reduce the fall in pH,
notably
> sodium bicarbonate.
>
> Turns out this is all wrong. Lactic acid and the lower pH actually helps
keep
> the muscles working during periods of fatigue. The real culprits in
causing
> fatiguing muscle to stop working are potassium and phosphate. The lower
pH
> helps the muscle cells continue to work in the presence of the altered
> potassium and phosphate concentrations.
>
> This actually makes sense, teleologically speaking. Generally, when the
body
> does something, it does it for a purpose. Why should humans evolve to
produce
> a toxin which causes muscle to shut down? It makes much more sense that
lactic
> acid helps the muscle fibers to compensate for ionic imbalances which
occur
> during extreme exercise. So, actually, the athlete would be, at least in
> theory, better served by INCREASING lactate concentration, rather than
> decreasing it. Yogurt is a very good source of lactic acid. I'm going to
> start experimenting with "yogurt loading" right before I swim (I'm really
good
> at exercising with food in my stomach).
>
> The lactic acid may still be the culprit in one thing...that being the
muscle
> "burn." The lactic acid, when it leaks out of the local muscle cells in
high
> concentrations, my activate sensory nerve receptors which are sensitive to
> changes in pH. Again, it makes teleological sense for the body to have an
> "early warning" system for work overload. The lactic acid "burn" is a
signal
> to slow down.
>
> So lactic acid is not a villain, but rather a hero. Triple threat.
Storage
> form of energy. Lowers pH to allow muscle cells to continue to function
with
> altered potassium and phosphate levels. Warns body that there is
impending
> overload.
>
> There's probably a commercial opportunity in this. From "Power Yogurt" to
"I
> [heart] lactate" T shirts.
>
> - Larry

08-23-2004, 07:09 PM

could you email me the article it the science web site requires a account be
setup.

Thanks,

"Bob Schroedter" <[Only registered and activated users can see links. ]> wrote in message
news:uJPVc.12496$%[Only registered and activated users can see links. ].. .
> from a post on another newsgroup...
>
> Full Text : Allen and Westerblad, PHYSIOLOGY: Enhanced: Lactic Acid--The
> Latest Performance-Enhancing Drug, Science 2004 305: 1112-1113
> [Only registered and activated users can see links. ]
>
>
>
> ----- Original Message -----
> From: "Larry Weisenthal" <runnswim@aol.comnet>
> Newsgroups: rec.sport.swimming
> Sent: Saturday, August 21, 2004 4:57 AM
> Subject: Lactic Acid Paradigm Shift
>
>
> > On NPR Friday there was an in depth science story which was of
monumental
> > importance to exercise physiology. Published in Science. I haven't
read
> it
> > yet, but basically, it goes like this:
> >
> > Conventional thinking is that lactic acid is something bad...which
> degrades
> > muscle performance. Lactic acid forms when there is so much sugar
> metabolism
> > that the mitochondria of the cells can't handle it. Glucose is degraded
> to
> > pyruvate to make ATP to power the muscle contraction. The pyruvate then
> enters
> > the mitochondria to go into the Krebs cycle to make still more ATP. But
> when
> > pyruvate is produced so fast that it can't be processed by the
> mitochondria, it
> > gets converted to lactic acid, which is either stored in the muscle cell
> or
> > washed away into the blood stream. Lactic acid is a temporary storage
> form of
> > potential energy. Once the mitochondria have caught up, lactic acid can
> be
> > metabolized in the mitochondria to produce ATP to power muscles. In
fact,
> the
> > preferred energy source for cardiac muscle is lactic acid, although all
> muscles
> > can "burn" it to produce ATP.
> >
> > But the "problem" is that lactic acid lowers the pH of the muscle cells.
> > Conventional wisdom is that this is bad and that the falling pH is
> responsible
> > for "poisoning" muscle contraction. So this has led to all sorts of
> theories
> > about training improving the "buffer capacity" of muscle cells (you can
> read
> > about this everywhere, including in Maglischo). And it has led to all
> sorts of
> > nutritional supplements to imrpove buffering to reduce the fall in pH,
> notably
> > sodium bicarbonate.
> >
> > Turns out this is all wrong. Lactic acid and the lower pH actually
helps
> keep
> > the muscles working during periods of fatigue. The real culprits in
> causing
> > fatiguing muscle to stop working are potassium and phosphate. The lower
> pH
> > helps the muscle cells continue to work in the presence of the altered
> > potassium and phosphate concentrations.
> >
> > This actually makes sense, teleologically speaking. Generally, when the
> body
> > does something, it does it for a purpose. Why should humans evolve to
> produce
> > a toxin which causes muscle to shut down? It makes much more sense that
> lactic
> > acid helps the muscle fibers to compensate for ionic imbalances which
> occur
> > during extreme exercise. So, actually, the athlete would be, at least
in
> > theory, better served by INCREASING lactate concentration, rather than
> > decreasing it. Yogurt is a very good source of lactic acid. I'm going
to
> > start experimenting with "yogurt loading" right before I swim (I'm
really
> good
> > at exercising with food in my stomach).
> >
> > The lactic acid may still be the culprit in one thing...that being the
> muscle
> > "burn." The lactic acid, when it leaks out of the local muscle cells in
> high
> > concentrations, my activate sensory nerve receptors which are sensitive
to
> > changes in pH. Again, it makes teleological sense for the body to have
an
> > "early warning" system for work overload. The lactic acid "burn" is a
> signal
> > to slow down.
> >
> > So lactic acid is not a villain, but rather a hero. Triple threat.
> Storage
> > form of energy. Lowers pH to allow muscle cells to continue to function
> with
> > altered potassium and phosphate levels. Warns body that there is
> impending
> > overload.
> >
> > There's probably a commercial opportunity in this. From "Power Yogurt"
to
> "I
> > [heart] lactate" T shirts.
> >
> > - Larry
>
>

08-26-2004, 09:05 AM

PHYSIOLOGY
Lactic Acid The Latest
Performance-Enhancing Drug
David Allen and Hákan Westerblad

The 2004 Athens Olympics will undoubtedly see many records broken.
Improved performances will be attributed to better training, superior
genes, or the use of performance-enhancing drugs, both legal and
illegal. From a physiological perspective, one of the major limits to
improved performance is the decline in muscle function as muscles are
used intensively and repeatedly—a phenomenon called muscle fatigue.
Many of the approaches used by athletes to enhance their performance,
such as creatine supplementation, carbohydrate loading, and training
at high altitude, are targeted at the various pathways that
con-tribute to muscle fatigue. For many athletes, coaches, and sports
commentators, muscle fatigue and the accumulation of lactic acid
(generated from the anaerobic breakdown of glycogen) are more or less
synonymous. However, the importance of lactic acid in muscle fatigue
is now under scrutiny (1): On page 1144 of this issue, Pedersen et al.
(2) present a further challenge to the traditional view with their
demonstration that lactic acid, in fact, has beneficial effects on the
performance of fatigued muscles. They show in rat muscle fiber
preparations that lactic acid influences the activity of chloride ion
(Cl-) channels, which in turn sustains the action potentials that are
necessary for muscle contraction.
It was A. V. Hill in 1929 who proposed that the accumulation of lactic
acid in muscles contributes to muscle fatigue (3). Using preparations
of isolated frog muscle removed from solution and kept in nitrogen,
Hill showed that, following electrical stimulation, mechanical
performance gradually declined as the muscle accumulated large amounts
of lactic acid. However, if the muscle preparation was transferred to
a saline solution equilibrated with nitrogen, which enabled the
lac-tic acid to diffuse away, muscle performance improved. Such
experiments, and their equivalents in mammalian muscle, suggested that
accumulation of intracellular lactic acid
might be a principal cause of muscle fatigue. The theoretical basis
for this idea was provided by Fabiato (4), who showed that increased
intracellular acidification (acidosis) of muscle due to accumulation
of lactic acid blocked force production by the muscle's contractile
proteins.
Doubts about the importance of lactic acid in muscle fatigue, however,
have accrued since these early studies. For in-stance, humans
deficient in the enzyme myophosphorylase are unable to break down
glycogen or accumulate lactic acid, but their muscles fatigue more
rapidly than normal (5). The direct depressant effect of acidosis on
contractile proteins, clearly evident at or below room temperature, is
greatly reduced at body temperature (6). Work on single muscle fibers
has shown that when muscle cells are intentionally rendered acidic,
the rate of fatigue remains unchanged (7).
It was Nielsen and his colleagues who ushered in a new phase in our
understanding of the effects of muscle acidosis (8). They argued that
the accumulation of extracellular potassium ions (K+) is a key
component of muscle fatigue and showed that force in an isolated
muscle declined steeply when the K+ concentration in-creased.
Importantly, if the muscle was rendered acidic, much of the decline in
force was reversed and was accompanied by recovery of action potential
generation.
In the new study, Pedersen et al. (2) take this observation a step
further using a preparation of "skinned" single muscle fibers from the
rat. In their preparation, the surface membrane of the muscle fiber is
removed (mechanical skinning), but the internal network of tubules in
the fiber (T-
tubules) seals over and retains its function-al connection to the
sarcoplasmic reticulum. This intriguing preparation can be activated
in various ways. Crucially for these experiments, electrical
stimulation generates action potentials in the sealed T-tubules and
causes normal release of calcium ions (Caz+) from the sarcoplasmic
reticulum, resulting in muscle contraction.
The investigators noted that when action potentials stimulated Cat+
release, mild de-polarization of the T-tubules caused a large
reduction in contractile force but, as Neilsen et al. found (8), this
effect could be partially re-versed by acidosis. Their key observation
is that this effect could be eliminated by removing Cl- from the
solution bathing the muscle preparation, suggesting that acidosis
exerts a beneficial effect on Cl- channel activity. A central feature
of the new mechanism is that the accumulation'of extracellular K+
results in action potentials becoming a less effective trigger of Caz+
release in working muscles. Acidosis reduces this effect by decreasing
the contribution of Cl- channels, which act to clamp the membrane
potential near the chloride reversal potential. Because the chloride
reversal potential is near the resting membrane potential, the effect
of Clchannel activity is to increase the amount of sodium ion (Na+)
current necessary to generate an action potential, which then triggers
Cat+ release. This mechanism will only operate under conditions in
which the amplitude of the action potential has be-come a
rate-limiting step for muscle activity. Unfortunately, it is not easy
to establish whether this is the case in different types of muscle
fatigue.
The Pedersen et al. findings add to the complexity of the contribution
of intracellular and extracellular acidosis to muscle performance.
Generated by the anaerobic breakdown of glycogen, lactic acid is, from
the standpoint of active muscle, an inefficient way to produce ATP. An
increase in intracellular acidosis will affect the function of many
intracellular proteins besides contractile proteins, but we do not yet
know which of these are important for muscle contraction. Lactic acid
is ferried out of muscle cells by lactate transporter proteins,
creating an extracellular acidosis, which probably contributes to the
painful sensations of muscle fatigue experienced by athletes. Once in
the circulation, lactate
can be metabolized by other tissues and may be involved in the
regulation of the respiratory and circulatory systems.
Fatigue has many sources that may be present at different sites in
muscle cells. Many constituents of muscle metabolism (lactic acid,
glycogen, phosphocreatine, in-organic phosphate, ATP, Cat+, Na+, K+)
change during fatigue and, for each of these, we need to know which
proteins are affected and how these proteins regulate muscle
contraction. Equally important is the effect of multiple cellular
changes on muscle activity in the intact animal. Athletes and trainers
who keep abreast of these issues may potentially be able to modify
aspects of their training or performance in ways that give them a
competitive edge.

References
1. H. Westerblad et aL, News Physiol Sci. 17, 17 (2002).
2. T. H. Pedersen et at., Science 305, 1144 (2004).
3. A. V. Hill, P. Kupalov, Proc. R. Soc. London Ser. B 105,
313 (1929).
4. A. Fabiato, F. Fabiato, J. Physiol (London) 276, 233 (1978).
5. E. B. Cady et aL, J. Physiol (London) 418, 311 (1989).
6. E. Pate et aL, J. Physiol. (London) 486, 689 (1995).
7. J. D. Bruton et aL, J. Appl. Physiol. 85, 478 (1998).
8. O. B. Nielsen et al, J. PhysioL 536, 161 (2001).

1112-1113 20 AUGUST 2004 VOL 305 SCIENCE [Only registered and activated users can see links. ]

D. Allen is at the Institute of Biomedical Research, University of
Sydney, NSW 2006, Australia. H. Westerblad is at the Karolinska
Institute, S-171 77 Stockholm, Sweden. E-mail: [Only registered and activated users can see links. ].
edu.au, [Only registered and activated users can see links. ]

"Tom DiMauro" <[Only registered and activated users can see links. ]> wrote in message news:<[Only registered and activated users can see links. ]>...
> could you email me the article it the science web site requires a account be
> setup.
>
> Thanks,
>
>
> "Bob Schroedter" <[Only registered and activated users can see links. ]> wrote in message
> news:uJPVc.12496$%[Only registered and activated users can see links. ].. .
> > from a post on another newsgroup...
> >
> > Full Text : Allen and Westerblad, PHYSIOLOGY: Enhanced: Lactic Acid--The
> > Latest Performance-Enhancing Drug, Science 2004 305: 1112-1113
> > [Only registered and activated users can see links. ]
> >
> >
> >
> > ----- Original Message -----
> > From: "Larry Weisenthal" <runnswim@aol.comnet>
> > Newsgroups: rec.sport.swimming
> > Sent: Saturday, August 21, 2004 4:57 AM
> > Subject: Lactic Acid Paradigm Shift
> >
> >
> > > On NPR Friday there was an in depth science story which was of
> monumental
> > > importance to exercise physiology. Published in Science. I haven't
> read
> it
> > > yet, but basically, it goes like this:
> > >
> > > Conventional thinking is that lactic acid is something bad...which
> degrades
> > > muscle performance. Lactic acid forms when there is so much sugar
> metabolism
> > > that the mitochondria of the cells can't handle it. Glucose is degraded
> to
> > > pyruvate to make ATP to power the muscle contraction. The pyruvate then
> enters
> > > the mitochondria to go into the Krebs cycle to make still more ATP. But
> when
> > > pyruvate is produced so fast that it can't be processed by the
> mitochondria, it
> > > gets converted to lactic acid, which is either stored in the muscle cell
> or
> > > washed away into the blood stream. Lactic acid is a temporary storage
> form of
> > > potential energy. Once the mitochondria have caught up, lactic acid can
> be
> > > metabolized in the mitochondria to produce ATP to power muscles. In
> fact,
> the
> > > preferred energy source for cardiac muscle is lactic acid, although all
> muscles
> > > can "burn" it to produce ATP.
> > >
> > > But the "problem" is that lactic acid lowers the pH of the muscle cells.
> > > Conventional wisdom is that this is bad and that the falling pH is
> responsible
> > > for "poisoning" muscle contraction. So this has led to all sorts of
> theories
> > > about training improving the "buffer capacity" of muscle cells (you can
> read
> > > about this everywhere, including in Maglischo). And it has led to all
> sorts of
> > > nutritional supplements to imrpove buffering to reduce the fall in pH,
> notably
> > > sodium bicarbonate.
> > >
> > > Turns out this is all wrong. Lactic acid and the lower pH actually
> helps
> keep
> > > the muscles working during periods of fatigue. The real culprits in
> causing
> > > fatiguing muscle to stop working are potassium and phosphate. The lower
> pH
> > > helps the muscle cells continue to work in the presence of the altered
> > > potassium and phosphate concentrations.
> > >
> > > This actually makes sense, teleologically speaking. Generally, when the
> body
> > > does something, it does it for a purpose. Why should humans evolve to
> produce
> > > a toxin which causes muscle to shut down? It makes much more sense that
> lactic
> > > acid helps the muscle fibers to compensate for ionic imbalances which
> occur
> > > during extreme exercise. So, actually, the athlete would be, at least
> in
> > > theory, better served by INCREASING lactate concentration, rather than
> > > decreasing it. Yogurt is a very good source of lactic acid. I'm going
> to
> > > start experimenting with "yogurt loading" right before I swim (I'm
> really
> good
> > > at exercising with food in my stomach).
> > >
> > > The lactic acid may still be the culprit in one thing...that being the
> muscle
> > > "burn." The lactic acid, when it leaks out of the local muscle cells in
> high
> > > concentrations, my activate sensory nerve receptors which are sensitive
> to
> > > changes in pH. Again, it makes teleological sense for the body to have
> an
> > > "early warning" system for work overload. The lactic acid "burn" is a
> signal
> > > to slow down.
> > >
> > > So lactic acid is not a villain, but rather a hero. Triple threat.
> Storage
> > > form of energy. Lowers pH to allow muscle cells to continue to function
> with
> > > altered potassium and phosphate levels. Warns body that there is
> impending
> > > overload.
> > >
> > > There's probably a commercial opportunity in this. From "Power Yogurt"
> to
> "I
> > > [heart] lactate" T shirts.
> > >
> > > - Larry
> >
> >

09-13-2004, 06:00 AM

Lactic acid has never been poison in the pure sense of the word
Trained properly you can fuel with it.

The article is not revolutionary!

"Tom DiMauro" <[Only registered and activated users can see links. ]> wrote in message
news:[Only registered and activated users can see links. ]

> could you email me the article it the science web site requires a account be
> setup.
>
> Thanks,
>
>
> "Bob Schroedter" <[Only registered and activated users can see links. ]> wrote in message
> news:uJPVc.12496$%[Only registered and activated users can see links. ].. .
> > from a post on another newsgroup...

> >
> >

--
Posted via Mailgate.ORG Server - [Only registered and activated users can see links. ]

09-13-2004, 04:49 PM

The article makes that point exactly. The research has been around for a
while but the winds of change are slow in some fitness and healthcare
circles.

"Kenneth Burres" <[Only registered and activated users can see links. ]> wrote in message
news:38416e18965faf4ac22dd9b6730fee9d.32275@mygate .mailgate.org...
> Lactic acid has never been poison in the pure sense of the word
> Trained properly you can fuel with it.
>
> The article is not revolutionary!
>
> "Tom DiMauro" <[Only registered and activated users can see links. ]> wrote in message
> news:[Only registered and activated users can see links. ]
>
> > could you email me the article it the science web site requires a
account be
> > setup.
> >
> > Thanks,
> >
> >
> > "Bob Schroedter" <[Only registered and activated users can see links. ]> wrote in message
> > news:uJPVc.12496$%[Only registered and activated users can see links. ].. .
> > > from a post on another newsgroup...
>
> > >
> > >
>
>
>
>
> --
> Posted via Mailgate.ORG Server - [Only registered and activated users can see links. ]