Caffine and Running Performance
Reprinted from:
Peak Running Performance
In the late 1970s and early 1980s, marathon runners began to use
caffeine with the intent of improving their race performances. The notion
existed at this time that caffeine intake released free fatty acids into
the bloodstream and thus increased the usage of fat by one's muscles,
sparing the body's limited glycogen stores essential to a marathoner's
energy supply.
It was further believed that "hitting the wall" - which occurs when
glycogen stores become depleted - could be delayed or even avoided,
allowing race times to improve. This article will examine some of the
research that has been conducted over the last fifteen years to see
whether or not caffeine can actually improve exercise performance.
Caffeine and Exercise
Caffeine has three main effects on the body as it relates to exercise.
Caffeine acts: (1) as a stimulus to the central nervous system, (2) to
decrease the contractile threshold of a muscle, allowing a smaller
stimulus to elicit a muscle contraction, and (3) to increase the
mobilization of free fatty acids in the blood stream.2
Free fatty acids are the portion of fat that can be burned as fuel by
the muscles, and as an energy resource they are of major importance to
marathoners and other distance runners.
Caffeine's Benefits to Distance Runners
Due to the increase of free fatty acids that occurs as a result of
caffeine ingestion, caffeine was seen as beneficial to long distance
runners, especially marathoners.
Physiologically speaking, as you run, your muscles use both fat and
glycogen as fuel. Theoretically, the body has an unlimited supply of fat
for distance running purposes. However, the natural tendencies of our
bodies are to use mostly muscle glycogen as fuel in the first 90 minutes
of running.
Caffeine increases the use of fat as fuel, thus sparing our bodies'
limited supply of muscle glycogen. After about 90 minutes, the glycogen
stores can become depleted, causing you to slow down (also known as
"hitting the wall") as your body switches to fat as the primary fuel.
By performing extra long runs (more than 90 minutes in duration), not
only will you be able to (1) build thick, new networks of oxygen-carrying
capillaries, (2) increase the number and energy-producing capacity of your
muscle cells' mitochondria, (3) safely recruit and train fast-twitch
muscle fibers to gain greater endurance potential, but you will also be
able to (4) teach your body to begin using more fat as a fuel earlier in
your runs, thereby delaying the depletion of your muscle glycogen and
ultimately increasing your endurance (your ability to run for a longer
period of time).
Therefore, if you could further increase the body's use of fat as a
fuel earlier in your training runs (through caffeine ingestion), you could
benefit from being able to train longer distances and race farther before
slowing down. This is because delaying the use of glycogen will allow you
to maintain a given pace longer before fatigue sets in.
