Caffeine may negatively affect your performance as a triathlete, according to trifuel.com. The intake of caffeine can lower your body's pH level. Acidic body chemistry can lead to any of the following: faster fatigue, slower recovery, inability to concentrate, frequent illness, and chronic muscle pain. While it's still a good idea to have a jolt right before an endurance event, don't over do it. And take a look at our best tips for training like a real athlete.