You can get hot even when it’s not hot outside. Climbing or riding the trainer, for example. Why? Your engine is only 20 - 40% efficient. Of the calories your muscles burn, 60 - 80% produce heat, not forward motion. You need to disperse that heat or your core temperature will start to rise and your performance will diminish. You may start to suffer from heat exhaustion, which, if not treated, could develop into heat stroke, a potentially fatal condition.

Performance falls off even at moderately warm temperatures. A group of trained cyclists was asked to ride at the same perceived effort they would expend if riding a 20- to 40K-time trial. They repeated the trial rides at temperatures of 59, 77, 95F (15, 25 and 35C). Based solely on perceived effort, their power output declined as the temperature rose. At what you and I would consider a comfortable riding temperature they weren’t performing as well as at a cooler temperature!

Increasing your sweat rate and radiation from increased blood flow to the skin account for about 85% of your body’s cooling.

• Moderate Dehydration Doesn’t Hurt Performance—Pro stage racers ride so hard that their guts can’t absorb enough fluid to replace all that they are losing in sweat. Race rules also restrict when a rider can get a bottle toward the end of a stage. Although somewhat dehydrated, the pros sprint quite well!.
  Information on: 12 hydration myths
• Start Out Fully Hydrated—Drink enough each day that you urinate every few hours with an ample, clear stream.
• Drink to Satisfy Thirst—We used to be told, “Drink before you’re thirsty, eat before you’re hungry.” Scientists now advise just drinking enough to satisfy thirst; drinking too much risks developing low blood sodium (hyponatremia), a potentially fatal condition. Information on: Hyponatremia.
• Drink Don’t Dowse—Because your core temperature (not your skin temperature) is the limiter on performance, drink all the fluid in your bottles to stay hydrated. Of course, if you’re at a mini-mart, etc., pouring more water on your head is a very effective way to cool off.
• Eat Sodium—Sodium is the primary electrolyte lost in sweat and the only one you need to replace. A quart of sweat contains approximately 800 mg of sodium (although the amount varies widely), which is one-half of the Daily Recommended Intake in your diet! The amounts of potassium, calcium and magnesium are all less than 5% of the recommended daily intake.
• Drink Electrolyte Drinks—Electrolyte drinks help to replace the sodium you are losing and the glycogen you are burning. However, they don’t contain enough electrolytes to replace all that is lost in sweat. You can also develop hyponatremia from drinking too much electrolyte drinks.
• Make Your Own Electrolyte Drinks—Here’s a recipe to make your own that does contain all the electrolytes you need: homemade electrolyte drink.
• Electrolyte Supplements Aren’t Necessary—Sodium is the only electrolyte you need to replace and you can get plenty from real food like V-8 or tomato juice, crackers and pretzels (chips are too salty), deli turkey, etc.
• Beer Is Bad—Although beer contains calories and fluid, it’s a bad rehydration beverage. Most of the calories are empty calories from alcohol, not carbohydrates, which is the source of the glycogen you burn while riding. The alcohol causes you to urinate more and you lose more water than you drink.
• Rehydrate By Weight—Weigh yourself nude before you ride and nude again afterward. The difference in weight is the amount of fluid you haven’t replaced during the ride. One pound equals approximately one pint. For every pound you’ve lost drink 1.5 pints of water or sports drink, enough to rehydrate you and meet your ongoing hydration needs.
• Symptoms of Heat Exhaustion—Know the symptoms of heat exhaustion:
  Information on: Heat exhaustion
• Symptoms of Heat Stroke—Heat stroke is a medical emergency. Know the symptoms and if someone develops them, call 911.
  Information on: Heat stroke
• Symptoms of Hyponatremia—Hyponatremia, if untreated, can also become fatal. Know the symptoms:
  Information on: Hyponatremia

The bottom line:

• Develop the habit of drinking frequently during the day and evening so that you are fully hydrated before exercise.
• During exercise drink whenever you are thirsty, but not more.
• After sweaty exercise, particularly if your clothes are white with salt, eat salty snacks.

Remember: riding in the heat isn’t just about riding when it’s hot outside.

More Information

• Cycling in the Heat Bundle Parts 1 and 2 — 41 pages for $8.98, a 10% discount, from RoadBikeRider.com. It includes:
1. Cycling in the Heat Part 1: Ride Management — How to acclimate, how to ride in the heat, what to eat and heat-related problems. 19 page eArticle for just $4.99 from RoadBikeRider.com.
2. Cycling in the Heat Part 2: Hydration Management — Develop your personal hydration and electrolyte plan. 21 page eArticle for $4.99 from RoadBikeRider.com.
• Cramping: How to prevent and deal with cramps — my 10-page eArticle for $4.99 from RoadBikeRider.com.
• Nutrition for 100K and Beyond: Cycling nutrition, hydration and electrolytes — my 16-page eArticle for $4.99 from RoadBikeRider.com.
• Eating & Drinking Like the Pros: Expert advice on cycling nutrition and how to make your own healthy nutrition at lower cost — my 15-page eArticle for $4.99 from RoadBikeRider.com.
• Other articles by Coach Hughes from RoadBikeRider.com