How Does Caffeine Extend Endurance?
Caffeine is a remarkable product for serious athletes because it extends endurance four ways:

  1. Caffeine improves endurance by sparing muscle glycogen.  Your muscles contain a fixed amount of glycogen, the muscle’s energy source.  When glycogen levels are depleted, you hit the wall or bonk.  Caffeine may preserve muscle glycogen by increasing the use of fat as an energy source.
  2. Caffeine may extend endurance through a different mechanism.  When caffeine is combined with carbohydrate in a sports drink it stimulates the metabolism of carbohydrate into energy source.
  3. Caffeine increases the absorption rate of the carbohydrate, which means faster delivery of carbohydrate to working muscles where it could be converted into energy.
  4. The brain plays an important role in extending endurance.  Fatigue signals emanating from the brain send messages to our muscle telling us we are tired and should stop.  Caffeine, by blocking these specific signals, delays fatigue and thereby extends endurance.

However, there are some myths about caffeine that many athletes believe. The first myth is that caffeine, because of its diuretic effect, causes dehydration.  You can have up to five cups of coffee without affecting hydration levels.  In other words you can consume quite a few caffeinated sports drinks and gels.

The second myth is that caffeine causes GI problems. Although sports drinks cause more GI problems than water, sports drinks with caffeine caused no more problems than sports drink without caffeine.