Hot Weather Cycling, Pt. 2: Hydration and Electrolytes
Most of the heat you feel cycling in the heat is produced by your muscles, not the ambient conditions. Learn how to handle the heat even when it isnt hot outside.
by John Hughes
© John Hughes 2013, All Rights Reserved
John Hughes, the former director of the UltraMarathon Cycling Association and editor of UltraCycling, has been certified by the National Strength and Conditioning Association as a personal trainer and by USA Cycling as a coach.
You can get hot even when its 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 werent 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 bodys cooling.
[ Hot Weather Cycling:
Pt. 1 Training and Ride Management
| Pt. 2 Hydration and Electrolytes ]
Tips for Hydration When Its Hot
- Moderate Dehydration Doesnt Hurt PerformancePro stage racers ride so hard that their guts cant 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 HydratedDrink enough each day that you urinate every few hours with an ample, clear stream.
- Drink to Satisfy ThirstWe used to be told, Drink before youre thirsty, eat before youre 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 Dont DowseBecause 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 youre at a mini-mart, etc., pouring more water on your head is a very effective way to cool off.
- Eat SodiumSodium 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 DrinksElectrolyte drinks help to replace the sodium you are losing and the glycogen you are burning. However, they dont 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 DrinksHeres a recipe to make your own that does contain all the electrolytes you need: homemade electrolyte drink.
- Electrolyte Supplements Arent NecessarySodium 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 BadAlthough beer contains calories and fluid, its 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 WeightWeigh yourself nude before you ride and nude again afterward. The difference in weight is the amount of fluid you havent replaced during the ride. One pound equals approximately one pint. For every pound youve lost drink 1.5 pints of water or sports drink, enough to rehydrate you and meet your ongoing hydration needs.
- Symptoms of Heat ExhaustionKnow the symptoms of heat exhaustion:
Information on: Heat exhaustion
- Symptoms of Heat StrokeHeat stroke is a medical emergency. Know the symptoms and if someone develops them, call 911.
Information on: Heat stroke
- Symptoms of HyponatremiaHyponatremia, 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 isnt just about riding when its hot outside.