Prepare Your Body for Hot Weather Mountain Biking

In summer, off-road cyclists must adjust to heat. Those who race on the national circuit must adjust to all kinds of hot weather--from the scouring, dry heat of the west to the wilting humidity of the south.

But heat stress hinders performance. It occurs when high humidity, radiant heat from the sun and elevated air temperature combine to impede your body's ability to dissipate heat. And it places considerable demands on your body's physiological control mechanisms.

Here are a few suggestions for preventing heat stress and adapting your program to the demands of summer cycling.

Build Up the Mileage

When the first hot spell of summer hits, gradually work your way up to several hours of exercise in the heat during your first few training sessions.

A gradual build-up to race distance and intensity should be completed by the seventh to 10th day of training. But everyone adapts differently to heat stress. In order to help your own unique body adjust, make sure you adapt gradually to a hot environment.

Get Used to the Temperature

Time of day is crucial. While you may have acclimatized to conditions in the morning, you still need to take steps if you are going to race during the heart of the day, when the heat is highest (noon to 3 p.m.). Over the last few days before an event, make a point of riding at that time of day to enhance your adaptive training. If you can only train in the morning, then wear extra clothing to purposely increase the heat stress.

Stay Hydrated

During hard training you will lose one to two quarts of fluid through perspiration each hour. If your fluid loss by sweat or urine exceeds your fluid intake, you will experience dehydration.

Body weight losses in the 3- to 4-percent range impair the body's ability to efficiently utilize oxygen. When dehydration causes more than 4- to 5-percent weight loss, your power will deteriorate tremendously. Always be aware that even during non-athletic activities in hot and humid conditions your fluid losses will typically range from one to 10 quarts every 24 hours.

To combat this, begin drinking even before you get on the bike. Drink eight ounces as you are pumping up your tires. During your ride, try to drink at least 8 to 12 ounces by sipping fluids every 20 minutes (make sure you sip fluids to avoid stomach discomfort).

If you cannot carry enough fluids in your water bottles, wear a back-mounted hydration system to ensure you drink enough. Such systems also keep fluids colder, and cool drinks tend to taste better, so you are apt to drink more. There is evidence that after-exercise carbohydrate-electrolyte beverages replace lost fluid in the blood at a slightly faster rate than pure water.

To make sure that you are properly hydrated, weigh yourself before and after hard training sessions in the heat, If you finish a training session with a weight loss of more than 3 to 4 percent, you should practice drinking more while on the bike.

You can assess the status of your body's fluid level by the volume of urine expelled. An adult's urine volume is about 1.2 quarts every 24 hours. If your daily urine volume is less than one quart a day, your body is conserving water and you should consume more fluids. Urine that is dark and yellow also indicates you may be dehydrated, and that your body's cells are being put under undue stress. If you experience frequent cramps, have your salt intake evaluated by a sports medicine physician or dietitian.

Keeping track of your body weight on a daily basis is an effective way to determine water loss. When you get out of bed in the morning, step on a scale. Record your weight in your training diary. If you experience a weight loss of 1 to 3 percent from the previous day's activity, avoid beginning a training session or competition until you are re-hydrated. Do this by drinking 16 ounces of fluid for each pound of body weight lost.

Dress Appropriately

Lastly, wear a white or light-colored jersey to reflect radiant heat as much as possible. Wear a jersey incorporating new materials that allow for greater transport of air and moisture flow in, out and over your hot body. Do not use oil-based sunscreens, which impede sweating.

Training, acclimatization and the proper use of sport drinks will help you perform your best in summer heat. The bottom line on all of this is to know your body and take care of it. If you use common sense and prepare properly for competition in the heat, nothing should stand between you and an excellent finish. Remember, you can't change the weather, but with a little planning, you can beat the heat.

Dr. Edmund R. Burke was among the pioneers in applying scientific principles to endurance sports training, especially cycling. As an exercise physiologist, he was responsible for several advances in sports drink formulation and almost single-handedly developed the subcategory of performance recovery drinks. A former director of the Center for Science, Medicine and Technology at the U.S. Cycling Federation in Colorado Springs, he worked with the U.S. Olympic cycling team during the 1980 and '84 Games. Dr. Burke is the author of 17 books on fitness, training and physiology, including the best-selling Optimal Muscle Recovery.

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