Dehydration. This is not the same as heat exhaustion. They can be related, but you can have one without the other. You will stop sweating and run out of energy if you are dehydrated. We call it wilting, because it’s the same as a plant wilting when it doesn’t have enough water.
Hydrating During the Carbo-loading Process: You have to drink more than usual in the last few days because carbohydrates require water before they can be stored in your muscles as glycogen.
You Can’t Load Up on Water. Drink just enough during the last several days that your urine is occasionally clear and copious. If your muscles cramp when you point your toes, you are probably not drinking enough. If you are peeing a lot once or twice an hour, however, you are over-hydrating, which can deplete your system of electrolytes.
Race Morning: Drink a little water during the night, especially if it’s hot and humid. Take a water bottle with you to the start of the race and sip a little, just to make sure you are fully hydrated. Avoid sugared drinks just before a race because your blood sugar level will already be high enough and more sugar can cause an adverse reaction.
During the Race: You should plan to take a small, hand-held bottle with you (it can be empty at the start). You won’t feel like drinking at first but once you start to sweat, your thirst will increase and you’ll need to drink almost constantly to keep up with water loss.
Wilting. If you lose three or four 12 oz. bottles worth of sweat (easy to do on a hot day in a long race) you’ll become dehydrated.
Sipping. In general, you should sip more or less constantly early in the race and gulp as your thirst dictates later in the race. Sip some liquid and wait until you feel it is out of your stomach before sipping again.
How Much to Drink. Don’t drink because you think you have to. You can easily get nauseated, especially if the water is too sweet. Remember, your body is a system. If the liquid is too sweet (or not salty enough), your system will reject it with nausea. Better to upchuck and start over than be nauseated.
Aid Stations: If you don’t carry a water bottle, stop at the aid stations and drink your fill as your thirst dictates. Otherwise, fill your bottle at the aid stations and carry it with you in your hand. Pour water over your head when it gets real hot.