This article is old news but the information will be eye-opening to some people and may revive this thread…
By GINA KOLATA
Published: May 16, 2006
Everyone who has even thought about exercising has heard the warnings about
lactic acid. It builds up in your muscles. It is what makes your muscles
burn. Its buildup is what makes your muscles tire and give out.
Coaches and personal trainers tell athletes and exercisers that they have to
learn to work out at just below their "lactic threshold," that point of
diminishing returns when lactic acid starts to accumulate. Some athletes
even have blood tests to find their personal lactic thresholds.
But that, it turns out, is all wrong. Lactic acid is actually a fuel, not a
caustic waste product. Muscles make it deliberately, producing it from
glucose, and they burn it to obtain energy. The reason trained athletes can
perform so hard and so long is because their intense training causes their
muscles to adapt so they more readily and efficiently absorb lactic acid.
The notion that lactic acid was bad took hold more than a century ago, said
George A. Brooks, a professor in the department of integrative biology at
the University of California, Berkeley. It stuck because it seemed to make
so much sense.
"It's one of the classic mistakes in the history of science," Dr. Brooks
Its origins lie in a study by a Nobel laureate, Otto Meyerhof, who in the
early years of the 20th century cut a frog in half and put its bottom half
in a jar. The frog's muscles had no circulation – no source of oxygen or
Dr. Myerhoff gave the frog's leg electric shocks to make the muscles
contract, but after a few twitches, the muscles stopped moving. Then, when
Dr. Myerhoff examined the muscles, he discovered that they were bathed in
A theory was born. Lack of oxygen to muscles leads to lactic acid, leads to
Athletes were told that they should spend most of their effort exercising
aerobically, using glucose as a fuel. If they tried to spend too much time
exercising harder, in the anaerobic zone, they were told, they would pay a
price, that lactic acid would accumulate in the muscles, forcing them to
Few scientists questioned this view, Dr. Brooks said. But, he said, he
became interested in it in the 1960's, when he was running track at Queens
College and his coach told him that his performance was limited by a buildup
of lactic acid.
When he graduated and began working on a Ph.D. in exercise physiology, he
decided to study the lactic acid hypothesis for his dissertation.
"I gave rats radioactive lactic acid, and I found that they burned it faster
than anything else I could give them," Dr. Brooks said.
It looked as if lactic acid was there for a reason. It was a source of
Dr. Brooks said he published the finding in the late 70's. Other researchers
challenged him at meetings and in print.
"I had huge fights, I had terrible trouble getting my grants funded, I had
my papers rejected," Dr. Brooks recalled. But he soldiered on, conducting
more elaborate studies with rats and, years later, moving on to humans.
Every time, with every study, his results were consistent with his radical
Eventually, other researchers confirmed the work. And gradually, the
thinking among exercise physiologists began to change.
"The evidence has continued to mount," said L. Bruce Gladden, a professor of
health and human performance at Auburn University. "It became clear that it
is not so simple as to say, Lactic acid is a bad thing and it causes
As for the idea that lactic acid causes muscle soreness, Dr. Gladden said,
that never made sense.
"Lactic acid will be gone from your muscles within an hour of exercise," he
said. "You get sore one to three days later. The time frame is not
consistent, and the mechanisms have not been found."
The understanding now is that muscle cells convert glucose or glycogen to
lactic acid. The lactic acid is taken up and used as a fuel by mitochondria,
the energy factories in muscle cells.
Mitochondria even have a special transporter protein to move the substance
into them, Dr. Brooks found. Intense training makes a difference, he said,
because it can make double the mitochondrial mass.
It is clear that the old lactic acid theory cannot explain what is happening
to muscles, Dr. Brooks and others said.
Yet, Dr. Brooks said, even though coaches often believed in the myth of the
lactic acid threshold, they ended up training athletes in the best way
possible to increase their mitochondria. "Coaches have understood things the
scientists didn't," he said.
Through trial and error, coaches learned that athletic performance improved
when athletes worked on endurance, running longer and longer distances, for
That, it turns out, increased the mass of their muscle mitochondria, letting
them burn more lactic acid and allowing the muscles to work harder and
Just before a race, coaches often tell athletes to train very hard in brief
That extra stress increases the mitochondria mass even more, Dr. Brooks
said, and is the reason for improved performance.
And the scientists?
They took much longer to figure it out.
"They said, 'You're anaerobic, you need more oxygen,' " Dr. Brooks said.
"The scientists were stuck in 1920."