The Body's Cooling System
Most people realize they sweat more when they exercise and that in order to stay healthy they need drink water. However, many people aren't aware of how much water they need to drink and why it's important to do so. When engaged in physical activity, body temperature rises as much as three degrees. Your body's natural cooling system – sweating -- kicks in to lower your body temperature. Under extreme exercise and heat stress, a body can lose half a gallon of water per hour! If the lost water is not replaced, dehydration occurs and serious consequences may follow.
When too much water is lost through sweating, your blood volume decreases. This decreases blood pressure, which in turn reduces blood flow between the muscles and skin. To overcome this, your heart rate increases. Because less blood reaches the skin, heat loss is reduced and the body overheats. Just like your car, your body can quit running.
If you fail to replace the water you lose, you run the risk of becoming dehydrated. When you are dehydrated by more than four or five percent of your body weight, your exercise performance declines by 20 to 30 percent. Not only that, the impact of dehydration on the cardiovascular system can produce heart problems in people with coronary heart disease and diabetes, as well. Lastly, dehydration is hard on the kidneys.
Sweating is not the only way you lose water. Another is through respiration; in other words, you lose water every time you exhale. This water loss increases as your physical activity increases because you breathe more.
How do you prevent your body from "breaking down?" It's simple: Put in as much water as what’s going out through your perspiration and respiration. Generally speaking, you should drink water before, during and after exercise. Drinking about two cups (16 fl. oz.) of water one hour before and one cup half an hour before is a good start. Then you should drink half a cup to one cup or more every 15 to 20 minutes (This amount varies depending on the air temperature, your body weight and how hard you are exercising.)
So drink up to keep your body running!