Sunny Skies Increase Danger of Dehydration

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While it’s still cold and gray in northern France, the sun is shining brightly as the Tour reaches the foothills of the Pyrenees. The rising temperatures will increase the difficulty of the next two stages and may have a significant impact on the outcome of the entire Tour.

Temperatures during Stage 11 were in the upper 80s, and it looks like the riders will face similar conditions when they tackle two of the hardest stages in the 2004 Tour de France on Friday and Saturday. Sweat rates are among the differences the riders will notice between the cool and rainy stages of the first week and the next few days. As temperatures climb, the body has to work harder to keep itself cool, and that means pumping more fluid to the skin so it can evaporate and keep core temperature from rising too high.

During a day like today, riders lose about 1.5 liters of water per hour of racing. For a four-hour stage, that adds up to an amazing six liters. If a rider were to race without replacing any fluids, he would lose over 13 pounds. Dropping just two percent of your body weight to fluid loss leads to diminished performance, meaning a 160-pound rider can only lose 3.2 pounds before beginning to suffer the debilitating effects of dehydration. Thirteen pounds is 7.5 percent of a 160-pound rider’s bodyweight, and losing that much water weight would send most athletes to the hospital.

To avoid dehydration in the increasing heat of southern France, riders will start increasing their fluid intake from about two bottles per hour to three. Some may even consume four. During the stage, the goal is to consume about 80 to 100 percent of the fluid volume you’re losing through sweat. After the stage, riders seek to consume 150 percent of the water weight they lost during the race. This means that if a rider lost two pounds (32 ounces) during the stage, he will drink at least 48 ounces of fluid in the hours afterward. You have to drink more water than you lost because your body is still losing water in the hours after you finish racing. If you were to only replace what you lost during the stage, you would still be behind because you didn’t account for normal water losses during that same period of time.

Fortunately, the first ten days of the Tour de France were neither hot nor extremely sunny, so riders like Lance Armstrong are not in the chronic dehydration situations they were in last year. In fact, in comparison to his performance at this point in the 2003 Tour de France, Lance Armstrong is considerably stronger. He’s been comfortable with the pace of the race, even when it has gotten difficult, and he’s looking forward to big mountains in the next few days.

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