Welcome to Sweating 101.
Question #1: During one hour of vigorous exercise, how much does the average person sweat?
Answer: One quart! As you can see, exercise saps a lot of water from our bodies. Start paying attention to your fluid intake 2-3 hours before you are going to exercise. Drink 2-3 cups of water during that time, and then drink another cup immediately before you start exercising. Without this extra water, your muscles will become dehydrated. Muscle movement depends on how hydrated you are, so if they are dry, they will not work as well. As a result, your workout will not be as productive as you would like. Once you start exercising, keep drinking water frequently. A good rule of thumb is to drink one cup every 15-20 minutes. Keep a water bottle with you. Take breaks to head to the water cooler. Do what it takes you keep yourself hydrated. Even when you are done exercising, you need to keep replenishing your fluid levels. It's recommended you drink another 2-3 cups within two hours after you have finished. Then drink water regularly afterwards. Do your body a favor and replenish that quart of fluids your body is losing while you work out. Your muscles will thank you later.
Exercise Extra: Staying properly hydrated helps make your workouts more productive.