http://www.nytimes.com/2007/10/11/fashion/11Best.html?ref=health
EXCERPTS
Economy can make the difference between being fast and being slow,
between winning and losing in swimming to skiing, cycling to speed
skating, running to rowing.
But economy is baffling. It seems to be physiological, but it is not
clear what exactly is involved. Is it an ability of muscles to use
energy, an ability to use a variety of muscles in concert, an ability
of nerves to activate certain muscles for a task while allowing other
muscles to relax, an ability of nerves to fire in near-perfect
patterns? Or is it all of these things in combination?
While many exercise physiologists believe, or hope, that economy
improves with training, they confess that it's not clear what kind of
training or how much it takes to make a difference.
They know that standard training programs, which emphasize speed and
distance, improve the other key factors in performance: VO2 max and
the anaerobic, or lactate, threshold, an indicator of how intensely a
person can exercise.
But economy is more of a mystery. In fact, there are only a few
documented cases of athletes whose economy improved. One was Paula
Radcliffe, the British marathoner. Every year for 11 years, starting
in 1992, she increased her running economy by about 1 to 3 percent. In
the end, she ran 40 seconds to a minute faster per mile, without
changing how much oxygen she took in.
....
But, Dr. Coyle said, "whether an average person running an hour a day
would experience the same benefit is the million-dollar question."
Researchers are finding that easy assumptions about exercise economy
just don't hold up under rigorous study.
Take the idea that you can tell who is an economical runner or cyclist
by watching the person perform. Not true, researchers say. The only
way to know is with tests in a lab.
Dr. Daniels showed this in a study in which he videotaped runners.
Then he sent the videos to coaches and biomechanics experts, and asked
which were the more economical runners.
"They couldn't tell, no way at all," he said.
But can runners become more economical if they change their form? The
surprising answer seems to be no, said Dr. Krahenbuhl. In fact, he
said, every study that asked what happened after runners changed their
natural form found that running economy declined.
It may take a long time for a change of form to result in better
economy, Dr. Daniels suggested.
....
Maybe economical runners or cyclists or swimmers are simply gifted in
general, researchers speculated. Perhaps whatever these athletes turn
to, they will be economical.
That, Dr. Daniels discovered, is not true.
He recently studied runners and measured their economy when they ran.
Then he measured it when they cycled, when they walked uphill at three
different inclines on a treadmill, when they stepped up and down on a
step, and when they cranked an ergometer with their arms. There was no
relationship between being economical at one activity and being
economical at another.
....
Dr. Coyle finds that the most economical cyclists have an abundance of
a particular type of muscle fiber, so-called slow twitch. It is not
known whether other types of muscle can convert to slow twitch with
training. But, he said, it may be that after years of training, nerves
are directed to allow more leg muscles to participate in pedaling. The
result might be greater riding economy.
"You might wind up changing the way your neuromuscular system is
wired," Dr. Coyle said. "It is a controversial area, but it makes
sense."
With swimmers, Dr. Coyle said, speed depends a great deal on
technique, which can improve to a certain extent with coaching and
training. Swimmers must overcome the drag of the water, and anything
that interrupts the fluid dynamics of their motion will cause them to
decelerate.
But physiological economy can also have a huge effect in swimming. Dr.
Daniels studied a woman who won an Olympic gold medal even though her
VO2 max was only average for a recreational athlete and was very low
for an elite athlete. Her gift? She wasted little energy, and that
skill more than compensated.