We're known for years that caffeine helps with performance. Many of us who are hardly world-class athletes can feel the difference just trotting around our neighborhoods. Have some caffeine before a workout, and you feel sprightlier and better overall. No caffeine, and it can be a slog jog the whole way.
The New York Times has a great article on the effects of caffeine on athletic performance. They quote Dr. Mark Tarnopolsky of McMaster University in Canada: “There is so much data on this that it’s unbelievable...It’s just unequivocal that caffeine improves performance. It’s been shown in well-respected labs in multiple places around the world.”
They also share research that shows how much caffeine you need--as little 1 milligram per kilogram of body weight. Diminishing returns start to happen at 9 milligram per kilogram of body weight. At that level, performance actually starts to decline.
Personally, I'm a Zipfizz addict. I way prefer that to coffee before a workout. But I have a little math to do to see if, before my next bike test, I need to have a cup of coffee too!