Injury Prevention - Temperature

33.9°C (93°F) SKIN TEMPERATURE
When air temperature approaches skin temperature your body tries to cool down by sweating. If the conditions are very humid, however, your sweat has more difficulty evaporating - the atmosphere has enough water in it already without taking your sweat as well. So, in humid conditions sweating doesn't cool you down that efficiently.

36.8°C (98.6°F) "CORE" BODY TEMPERATURE
Exercising raises the body's core temperature, so does hot, sunny weather. In these circumstances your body thermostat will try to cool things down so that your core temperature does not rise to dangerous levels.

38.9°C - 39.4°C (102°F - 103°F) DANGER LEVEL
If these cooling processes don't work, the body's core temperature may rise. At this level you will begin to experience heat exhaustion and start to feel some of the following: dizzy, tired, sick, headachy, short of breath, disorientated. If you continue to exercise at this point, you risk raising your core temperature to dangerous levels and you may begin to feel cramping, chills in the trunk and pounding in the head.

40.5°C - 41.1°C (105°F - 106°F) EMERGENCY LEVEL

This is the point at which you risk having heat stroke. The early signs of heat stroke are delirium or loss of consciousness, convulsions and dry skin. Heat stoke is extremely serious and can be fatal. This is an extreme medical emergency: even if you survive, you may suffer permanent brain damage.
==========================================

Injury Prevention - In the Heat

As tennis players, we are particularly at risk: tennis is usually played outside, in the summer months of the year, and the tennis circuit follows the sun around the world.

The Human Body

The human body is like an efficient thermostat, and most of the time we pay no more attention to its activity than we do to our central heating system. When the outside temperature threatens to lower the body's core temperature below a certain level, the body kicks in with a number of measures that are designed to reduce heat loss. When the outside temperature threatens to raise the core temperature, the body triggers a number of other measures to lose heat, like sweating and going red.

However, when you exercise for a long time in hot conditions - and especially in high levels of humidity - you put a lot of pressure on your body's thermostat, and there is a very real danger of overloading it.

Tips on Keeping Cool

Take extra care on hot, humid and sunny days. Avoid exercise during the hottest hours of the day (usually between 1000 hours and 1500 hours).

Avoid getting dehydrated. In the heat, you can lose up to two liters of water per hour of exercise. Water is the best drink to replace this liquid, but if you've been exercising for a long time, electrolyte replacement is good because it replaces the essential minerals lost in sweat. Most commercial sports drinks are designed to do this and six to eight gulps on each change over should be enough. Don't drink anything that has caffeine in it.

When and How Much to Drink

Drink about 600ml (1 pint) of water 30 minutes before your match. Then make sure you drink about 250ml (1 cup) of water for every 15-20 minutes of exercise (or at each change over in tennis). Weigh yourself before and after each workout - you shouldn't lose more fluid than 2 per cent of your weight.

Keep drinking after the match and check the color of your urine. Well-hydrated athletes will pass copious amounts of clear-colored urine. If your post-match weight is the same as your pre-match weight, that's another sign that you are well hydrated. You should replace every kilogram lost with one liter of water.

Dehydration

If you're thirsty you are already 2-3 per cent dehydrated. Any dehydration over 2 per cent will mean you perform less well. Good hydration not only decreases the risk of heat illness, it will help you perform better in the heat.

Put ice under your armpits and in the groin area to cool down quickly after a match or practice.

Wet clothes will make it more difficult for you to cool down (they restrict evaporation), so change your sweat-soaked clothes as often as allowed during the match. Wear clothing made from "wicking" material - it will draw the sweat away from your body and the material will remain dry - thus allowing your body to remain cool during exercise.

During the Match

You will lose much of your body's fluid and minerals in the form of sweat. You must replace these nutrients during play if you are to prevent dehydration, muscle cramps and dizziness. Water is still the best way to replace lost fluids, but sports drinks will help you to replace lost minerals (i.e. sodium and potassium). A 2:1 ratio of water to sport drinks is ideal.

Bananas are good foods to eat during a match: they're a good source of potassium and they're easily digested. Sports bars that are low in fiber and quick to digest are also good. Avoid cola drinks: they contain caffeine, which is a diuretic and therefore increases your fluid output. This is exactly what you are trying to prevent. Cola drinks may actually increase your chances of becoming dehydrated.

Keep out of the Sun

ATry to keep out of the sun before your match. Remember to use a sun block! With atmospheric changes, exposure to harmful UV radiation is increasing. Sun block is essential.

Be really careful if you have already experienced heat illness - if you've had it before, you are likely to have it again. You are also at risk if you have recently been ill, especially if you have a high temperature or have been vomiting or had diarrhea. Seek medical advice before you go on court.

Wear a hat that keeps the sun directly off your face and directs heat away from your body. A sun visor is best: it keeps the sun away, but does not retain heat. Wear loose, comfortable clothing of a light colors. This helps air to circulate close to the body to allow evaporation. Light colors reflect the sunlight (and reduce the radiation heat load).

Build up Your Tolerance

Spend some time getting used to exercising in the heat.

As your body gets used to working in a hot humid environment, it becomes more efficient at reducing the heat. These changes start a few days after arriving and peak at around 10-14 days.

Athletes who arrive earlier for an event will perform better in the heat.