Steamy evenings and tough workouts define the season - and raise your risk of heat induced injury dramatically. Only by heat hydrating properly can you perform well without overheating your body. Here's how and-why-you should drink on the run.

As you run, your muscles produce a tremendous amount of heat as they generate energy, and your body temperature surges upward. The heat produced by your muscles is then transferred to your blood as it moves through your muscles, and your blood carries the heat to your skin. Meanwhile, your sweat glands have shifted into high gear and soaked your skin with sweat. As sweat evaporates from the surface of your body, your body heat disapates with it. As a result, you stay cool... to a point.

This process occurs in all conditions hot or cold - but high heat and especially humidity complicate things, making it more difficult for your body to rid itself of excess heat.

And there's one other small problem: While sweating keeps you cool, it also dehydrates you. When you exercise in the heat, some of the water that normally courses through your bloodstream is shunted to the surface of your skin through your sweat glands. As a result, your blood volume begins to drop and your heart strains to pump your blood as its viscosity increases dramatically. The blood vessels leading into your skin constrict to prevent large drops in blood pressure as well. Once the blood flow to your skin diminishes, the blast of heat produced by your hard-working muscles can't be transported to the surface of your skin and your body temperature begins to climb. Simple as it sounds, drinking water will halt this chain reaction, keeping you cool and moving efficiently. The best way to ensure that this occurs is to drink adequately before, during, and after your runs.

The following are a few specifics that will lessen the summer heat's potentially negative effect on your running:

n You should drink 8-12 ounce glasses of water per day. In most cases, don't worry about taking in fluids during runs lasting 45 minutes or less.

n During longer workouts, drink 10-14 ounces of fluid immediately before you head out the door to run and then 3 to 4 ounces every 10 minutes thereafter. If you get stomach cramps or feel pressure on the left side of your belly initially, slowly increase your hydration to adapt to increasing levels.

n Monitor how you feel. If you have trouble maintaining your regular pace, slow down a bit. And if you become light-headed, slow down and walk for a while. If you experience chills, stop immediately, and find a shady place to sit down. You must allow your body to cool. Even though you're having chills, you're not cold. Your cooling system is about to shut-down and we don't want this to happen.

n Know yourself. Some people have more difficulty dealing with the heat than others do. If you're one of them, it doesn't mean you're a wimp or faint of heart; it simply means that you must train smart. Take it easy during the hot weather, especially if you've had trouble dealing with heat in the past. Once you become heat stressed, you are psycologically susceptible to it for the rest of your life.

n Run at sunrise or sunset. By running in the morning you avoid hot sunlight but usually face more humidity. By running in the afternoon you avoid high humidity but must brave the sun. Experiment to find out what works best for you. Try to avoid training from 11:30 a.m. to 4:00 p.m. when you must battle maximum humidity and the heat.

n Go out of your way to stay as cool as possible. Wear light loose clothing and opt for tree-lined streets or shaded trails.

Remember, it's nothing to brag about when you finish a race or workout totally depleted and dehydrated. When your blood gets thick due to dehydration it's impossible for your heart to maintain the same level of work as it would under optimal conditions. If the blood won't flow - you can't go.