While the debate on the merits of eight daily glasses of water continues, we know one thing for sure, nearly every cell of the human body contains water. Without water, cells don't function properly and they certainly don't function to their full potential during exercise. This is why it is important to hydrate before exercise.
In a recent study, physiologist Dan Judelson, PhD, observed that dehydrated exercisers completed three to five fewer reps per set, during strength-training sessions. Dehydration lowers hormone levels necessary for strong muscles. One to two hours prior to your workout, Judelson recommends drinking an ounce of water for every 10 pounds of body weight. If you weigh 120 pounds, you should drink 12 ounces of water before hitting the gym. Don't forget to sip water during your workout and drink enough to replenish the fluids your body lost through sweat.