Hot weather, as we all know, affects our performance. As our bodies bake beneath the punishing sun, they aren't just getting a sunburn. Our blood heats up, moving closer to the surface of the skin, where it is cooled through the mechanism of sweating. As a result, we have less blood in the middle of our bodies, where we need it most.

So if we have to work out in very hot weather, it's best to decrease the intensity of the workouts, or to play when the sun is not so intense. Whatever the choice, it's imperative to drink a lot of fluids before, during and after the competition, because thirst is not a true monitor of dehydration. By the time we become thirsty, we are already dehydrated.

The good news is that as summer moves into full swing, a phenomenon called acclimatization takes place. After a period of time working out in a hot, humid environment, we get better at it. No one knows what the mechanism is,
but it's real. In looking at how the weather (affects performance, humidity is not : to be overlooked, either. When the air is very humid, there is almost as much water in it as there is on the skin. Therefore, the sweat can't evaporate properly and the body can't cool down efficiently. When .our clothes become saturated with sweat, the effect is much the same, - and it is best to change into
something dry.

Heat injuries are essentially a failure of the cardiovascular system to respond to high external temperatures, and they occur on four different levels. The first is heat syncope-fainting or lighttheadedness. Because the body has sent all the blood to the surface, it's harder to get blood to the brain. At this stage, the best thing is just to lie down for awhile.

Then there are heat cramps-muscular tightening or spasming, usually in the lower extremities, although any muscle can be affected. Everyone remembers what happened to Michael Chang during the French Open a few years ago. When the muscles are overheated and become dehydrated, they go into a protective spasm. Heat cramps are not very serious, but they still can be painful.

Heat exhaustion occurs when sweating can no longer keep the internal body temperature near normal-the body temperature can reach as high as 103 degrees. The signs of heat exhaustion are weakness, lightheadedness, profuse sweating, nausea, vomiting, headaches and pains allover.
Usually, mental status remains pretty good, but heat exhaustion is ,tt; more serious and has to be treated quickly, with icewater in the armpits or cool water sprayed over the body.

When the body temperature exceeds 105 degrees, it is considered heat pyrexia, or heat stroke, and is a medical emergency. At this point, the patient is usually dry, because he is unable to sweat anymore, and has a beet red, disoriented appearance. He can actually have seizures, go into a coma and die. Heat stroke always requires immediate hospitalization.
Most of us won't see heat stroke on the court, but it is important to realize that these injuries occur on a spectrum, and if we don't respect heat cramps and the early signs of heat exhaustion,we can go on and have trouble.

All things being equal,the physically fit can stand hot weather a little bit better than the rest of us, because they generate less heat during the same workout. The overweight have less surface area per pound, so even though they may sweat a little bit more, they generate more heat. Therefore, being in shape before the warm season begins is a big plus.