Whole article at:

http://www.sciencedaily.com/releases/1999/07/990713073730.htm

Some clips:

"Leucine appears to have a specific, and apparently unique, impact on
skeletal muscle," said Donald K. Layman, a professor of nutrition. "It
stimulates muscle protein synthesis, provides fuel for the muscle and
helps to maintain blood glucose. What really surprised us was that its
activity is not seen when leucine or protein is consumed before or during
exercise. Instead it has a dramatic impact on protein synthesis during
the recovery period after exercise."

"It appears that leucine stimulates a signaling pathway somewhat like the
hormone insulin," Layman said. "It has been debated whether the action of
leucine was simply confused with the action of insulin. Our research
shows that there is a unique role of leucine, and that it runs almost
parallel to insulin. It appears that leucine stimulates the first step in
protein synthesis."

Based on the U. of I. research, Layman suggests that athletes:

-- Consume dietary protein of 1.4 to 2.0 grams per kilogram of body
weight per day to obtain the necessary level of leucine to help with
muscle development. An athlete weighing 175 pounds (79.5 kg) should eat
from 111 to 159 grams a day. (Convert pounds to kilograms by dividing by
2.2)

-- Immediately after exercise, consume a low-fat, protein-rich food such
as lean lunch meat or a protein drink or bar. Also include plenty of
carbohydrate-rich fluids.

-- Maintain a balanced diet that contains carbohydrates, fat and protein,
with the protein making up 30 percent of the calories, at every meal,
including snacks. Such a diet differs from current recommendations that
suggest meals of 60 percent to 70 percent carbohydrates and protein of
less than 20 percent of calories.

Editor's Note: The original news release can be found at
http://www.admin.uiuc.edu/NB/99.07/exerciseatstip.html