If you having been training for a least a while, you have probably heard that it is important to hydrate during training. What few athletes know, however, is how much fluid is adequate. What I observe is that the majority of athletes either just drink when they are thirsty or take a few sips when the coach tells them they can. But, the thirst mechanism lags behind the body's hydration level. This means by the time an athlete feels thirsty, he/she is already 1% dehydrated. Make it to 2% and you can see real performance detriments. On top of that, thirst is often stunted during activity due to the intensity of the training. Luckily, there is an easy way for every athlete to get an idea of where their fluid needs range.