Gabe Mirkin, M.D.
Caffeinated drinks increase endurance during long
events such as a marathon, triathalon or bicycle race. A study
from the University of Birmingham in England shows that caffeine
helps the body use more carbohydrates from drinks that you take
during exercise (Journal of Applied Physiology, June 2006).
Those who took sugared drinks with caffeine were able to absorb
and use 26 percent more of the ingested sugar than those who
took the same drinks without caffeine.
Previous studies show that caffeine helps athletes run
faster in both short and long-distance races. In short races, it
makes athletes faster by causing the brain to send messages
along nerves to cause a greater percentage of muscle fibers to
contract at the same time. In longer races, it delays fatigue by
preserving stored muscle sugar. Muscles get their energy from
sugar and fat in the bloodstream, and from sugar, fat and protein
stored in the muscles. When muscles run out of their stored
sugar, they hurt and become more difficult to coordinate.
Caffeine causes muscles to burn more fat, thus sparing stored
muscle sugar to delay fatigue.
Nobody really knows how much caffeine you can take in
without harming yourself. At rest, caffeine is a diuretic, but during
exercise it does not increase urination. Caffeine is a potent
stimulant that can cause irregular heartbeats in people who
already have heart disease, and raise blood pressure in people
with hypertension. Most research shows that it doesn't take
much more than one or two soft drinks to increase endurance.
Caffeine loses its beneficial effects with repeated exposure, so
athletes who want to gain maximum advantage from caffeine
during competition should avoid drinking caffeinated beverages
when they are not exercising.
September 15, 2006