I raced the Furnace Creek 508 through the Mojave Desert and Death Valley twice. I set a course record and won both times. I raced for over 30 continuous hours in each of those two races.
The 508-mile race, with 35,000 feet of climbing, is a qualifier for the Race Across AMerica. I wasn’t the fastest rider—many would have beaten me in a 40-km time trial. I wasn’t the lightest rider, nor was I the best climber.
But I was the smartest about riding in the heat!
Here’s what I learned about racing in the heat, which I’ve then tested as a coach working with ordinary roadies.
Sources of Heat
Even in very hot conditions, most of the heat is generated by your body, which is only about 25% efficient. For every four calories you consume, only one calorie provides energy to move you forward—and the other three calories produce heat. That heat must be dissipated from your body through primarily by sweat. Your body is like a car’s radiator. Blood circulates through your core, heats up and circulates to the skin where heat is dissipated via sweat.
The more aerobically fit you are, the more prepared you are to ride in the heat. Endurance riding increases plasma volume so that your body can better transfer heat from your core. Endurance riding increases your riding efficiency so that you ride with a lower heart rate under normal conditions. This means that when riding in the heat your heart rate can increase more to move blood through your radiator.
When you acclimatize, you start to sweat at a lower core temperature, and you sweat more, which keeps your core temperature lower. Your total blood supply increases so that you can sweat more while still maintaining blood flow to the muscles. Thus you disperse more heat both by convection (the increased blood flow to the skin) and by radiation.
You can bring about these changes through long endurance rides in hot conditions. You can also do specific heat adaptation sessions by riding hard enough to sweat heavily for 60 to 90 minutes. If you are already very fit, you can achieve significant acclimatization by riding this hard on four successive days. If you aren’t quite as fit, you may need as many as eight sessions with a rest day in between each session.
You may be tempted to spend most of your time in an air-conditioned environment and just ride for a few hours at a time in the heat. However, you don’t acclimatize fully unless you spend a lot of time in a hot environment, i.e., acclimatize passively.
About 75% of your energy makes you hotter rather than propelling you down the road. Even in relatively mild conditions you can overheat from internally generated heat! Simple rule: If you start to feel too hot, slow down!
Ride by Effort, Not Pace
Riding when you are hot drives up your heart rate, so your heart rate monitor doesn’t provide useful information about how hard your muscles are working. Because you can’t ride as hard when you are hot, gauge your effort by perceived exertion, not by your computer.
Because more blood flow is going to your skin to keep your brain, heart and other vital organs from overheating, less blood is available to your GI system transport food molecules to the rest of your body.
Fit Your Riding to the Conditions
Tailor your riding to the conditions at hand. In almost all conditions, mornings are a better choice than afternoons. If you need to ride longer, then two hours of endurance riding in the morning and two in the evening will provide more training benefit than four hours mid-day, because you can ride more briskly when it’s not as hot.
Try to time your outings based on the forecast, if you have a choice. If possible, take your rest day on the hottest day of the week.
Moreover, in urban and suburban areas, the sun warms the pavement and other surfaces so that the heat grows throughout the day, often making late afternoons and early evenings nearly as hot as mid-day in these environments. Later in the day ride in the countryside if you can.
Take Sun Seriously
Exposure to UV rays increases your risk of skin cancer. I’ve had three basal cell carcinomas removed. Fortunately, this type of skin cancer rarely spreads and is easily cut out. However, I’ve had two friends die of melanoma. When I was younger I thought that a cyclist’s tan lines were cool — not any more! My dermatologist, whom I see twice a year, recommends sun protective clothing because it doesn’t sweat off like sunscreen. You have to reapply sunscreen every 80 minutes to be protected, which takes a lot of time. I wear UPF 50+ sun protective clothing from Bouré. I wear either white arms or a long sleeve jersey and white legs. I use SPF 50 zinc oxide on any exposed skin.
Next week: hydration, dehydration and nature breaks.
Cycling in the Heat Bundle
You can learn more about the science of riding in the heat, and managing your fluids and electrolytes, in my two-part eArticle series:
- Cycling in the Heat, Part 1: Ride Management is 19 pages and covers how to acclimatize to hot conditions, how to train in hot months, what to wear, eat and drink, how to cool down if you overheat, and how to deal with heat-related problems.
- Cycling in the Heat, Part 2: Hydration Management is 21 pages and covers how to determine how much you should drink depending on your physiology and sweat rate, how best to replace your fluids and electrolytes, the contents of different sports drinks, how to make your own electrolyte replacement drinks, how to rehydrate after a ride, and how to deal with hydration-related problems.
The cost-saving bundled eArticles totaling 40 pages Cycling in the Heat Parts 1 and 2 are just $8.98 (a 10% savings) and, as always, just $7.64 for our Premium Members (includes their everyday 15% discount!).
- Cycling in the Heat, Part 1: Ride Management, 19 pages
- Cycling in the Heat, Part 2: Hydration Management, 21 pages
- Preventing and Treating Cramps, 10 pages
Detailed look into the causes of cramps, prevention techniques, and tips (both on-bike and off-bike, including photos) for breaking and flushing cramps.
- Eating and Drinking Like the Pros, 15 pages
What pro riders consume before, during and after a stage and the benefits for cyclists at all levels. Eating and drinking like the pros offers recreational riders the same nutritional benefits, which you can customize to your own needs at a fraction of the cost of commercial sports food and drink, if you choose to make our own. I worked with a professor of nutrition and an expert on hydration and electrolytes (both experts are cyclists) in creating recipes for both sports drinks and food.
Was this article helpful?
Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written nearly 30 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John's full bio.