Staying hydrated can help you perform better in your daily activities — especially at the gym.

You've heard the rule before: Drink eight glasses (or 64 ounces) of water each day. But when you work out, your body's demand for fluids increases even more, especially if you're exercising outdoors — or even warming up on the way to the gym — during warm summer months.

According to Dr. Sam J. Romeo, CEO of Romeo Medical Clinic, Inc., in Turlock, Calif., half the population is at least mildly dehydrated all the time. These people don't even know what a day feels like when they're fully hydrated. Drinking the right amount of water daily can lead to better decision-making skills and concentration, elevated moods and improved coordination. So just imagine how the benefits of proper hydration might affect your workout.

"Dehydration can decrease your strength, endurance and sports performance significantly," says Romeo. "If we have inadequate fluid intake, every cell and organ system in our body has to work harder. We have less blood volume, so the cardiovascular system has to increase our heart rate."

Plus, the more you sweat, the more fluid your body loses. To learn specifically how much water your body releases during a workout, weigh yourself without clothes before and after. Every half-pound of weight loss is equivalent to eight ounces of water lost, explains Romeo. Generally, to maintain a healthy hydration level it's important to drink 12 to 24 ounces before and after as well as about eight ounces every 20 minutes during the workout.

For shorter workouts — those lasting less than one hour — sports drinks are not necessary says Romeo. Longer, more intense workouts, though, require a combination of water and sports drinks to replace lost electrolytes and provide sugar for energy. To avoid the added calories, pick up any of the low-calorie sports drinks offered at Gold's Gym.

Don't worry about drinking too much; it's difficult for a healthy individual to over-hydrate. Those cramps that sometimes creep up during a workout are not generally caused by too much fluid consumption. In fact, they can sometimes be a sign of early dehydration, explains Mary Arnold, a USA Track & Field-certified running coach and two-time national qualifier in long-course triathlon. But most often the dreaded side stitch actually comes from undigested food or an irregular breathing pattern. "I have my athletes slow down or walk for 30 to 60 seconds to alleviate the cramp," says Arnold. "Walking with your hands stretched over your head — to stretch your diaphragm — and breathing deeply will get rid of the side stitch."

To beat the summer heat, maximize your workouts and get all the benefits of proper hydration on a daily basis. "Good hydration is not just a part of a workout: It is integral to a healthy lifestyle," Arnold says. "If you can't remember when you last had a glass of water, you should stop what you're doing and get one."