[Armstrong]

Hydration is an often overlooked element of prepping for a workout, but it's a must—particularly if you train intensely. "Hydration is a key factor in being able to push yourself to the limit," says Dymatize athlete Lawrence Ballenger. "You'll lose roughly 10 percent of your strength from being dehydrated." Studies have shown that even mild dehydration can also negatively impact your mood, mental acuity, and energy level—even if you don't feel thirsty.
Many people walk around all day long without realizing they're in a partially dehydrated state. The best way to avoid this is to make a water bottle a fixture in your life at home, on the road, at work—everywhere. Make sure you're sipping it throughout the day, so your tank is full when it comes time to train.

Quality intra-workout blends such as Dymatize's AminoPro contain electrolytes to help your body hold on to water during long workouts. If you've been debating whether to use an intra-workout supplement like BCAAs, consider this a point in their favor as well.

Remember: If you're thirsty, you're already dehydrated. At that point, stop sipping and get gulping, because gulping speeds up the rate at which your body absorbs water. Your best bet is to keep from becoming dehydrated in the first place!