Summer is officially here and rather than grumbling about the heat, you can use riding in the heat to improve your performance. You can also acclimate to the heat without long hot rides every weekend.
Heat Training Improves Performance by 6 to 8%!
Recent research shows that training in the heat yields more improvement than training in cool conditions! Twenty very fit club cyclists’ one-hour time trial performance was tested in 55F (13C) conditions. Twelve of the riders then trained for 10 days in hot conditions of 104F (40C) riding at 50% of VO2 max, i.e., hard enough to acclimate to the heat, but not hard enough to induce training adaptations for the highly trained athletes. The other eight did the same workouts at 55F (13C).
All the subjects were then retested. The 12 who had acclimated to the heat improved their time trial performance by 6% in cool conditions and 8% in hot conditions. The cyclists who trained in cool conditions showed no improvement. You may not want to train when it’s that hot; however, training when it’s in the 90s will still improve your performance. Note that the performance improvement came in a one-hour time trial. If high-end speed isn’t important to you then training hard when it’s hot will still help you to acclimate to riding in the heat.
Physiology of Heating and Cooling
Whether you are riding hard in moderate temperatures or cycling in hot weather, heat plays a role in both your performance and your enjoyment of the ride.
Why Do You Get Hot?
Seems obvious, right? It’s hot outside! But how can you overheat when it’s not so hot? Actually, you don’t overheat just because the ambient temperature is high. You overheat in several different ways and understanding these will help you ride better in the heat:
- Energy production.
The human body is only 20 to 40% efficient, which means that only 20 to 40% of the energy you get from eating is translated into forward motion. If you are a 160 lb. (73 kg) rider pedaling at 14 mph (22.5 km/h) for an hour, you are burning about 500 calories. Only about 100 to 200 calories are producing forward motion, and the remaining 300 to 400 calories are producing heat! You have to dissipate this heat or your core temperature will rise. Energy production and heat dissipation are the primary factors in overheating, whether you are riding on a 100 F (38 C) day or climbing hard when it’s only 60 F (15 C).
When the sun is out, you gain heat from direct radiation, as well as from radiation reflected from the pavement. You may also gain heat from radiation through diffuse clouds. Your body also radiates heat even when it’s hot outside. The higher the sun is in the sky the more radiation heats you up. You even gain heat from radiation if the surrounding air is cool. That’s why standing by a bonfire on a chilly night makes you feel warm! So even on a cool day, the bright sun contributes to your heat load.
You may dissipate heat when you exhale if your breath is warmer than the environment. If it’s really hot out you may actually gain heat through breathing. Hot air feels harder to breathe.
You also gain heat from conduction through hot parts of your bike. On one Race Across AMerica (RAAM) I sat on a black gel-filled seat cushion all day, and through conduction I developed second-degree burns on my butt, which caused me to drop out of RAAM. You lose heat through conduction when you apply an ice pack.
When it’s cool heat moves from your hotter body to the relatively cooler air through convection. If the air is hotter than you are, the reverse flow occurs and convection makes you hotter.
Increasing your sweat rate and radiation from increased blood flow to the skin account for about 85% of your body’s cooling. The rest comes from conduction and convection.
The fact that your energy metabolism is the primary source of heat has very important implications. Because your body generates so much heat, you could develop heat stress even in cool conditions! Riding at 14 mph (22.5 km/h) you are generating enough airflow to dissipate the heat. But what if you are climbing at 6 mph (10 km/h)? Even if it’s cool, you could overheat. For example, riding your trainer hard in a cool garage!
When you feel hot you also can’t ride as hard for psychological reasons—in short, it feels harder to ride when you are hotter. In another experiment, a group of trained cyclists were 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 15, 25 and 35C (59, 77, 95F). Based solely on perceived effort, their power output declined as the temperature rose.
So how hot is too hot? You can change both your physiological and psychological responses to heat by acclimating.
You acclimate actively by exercising in the heat, and acclimate passively by being in the heat.
If you are aerobically fit, your body is already better prepared to ride in hot conditions. When hot weather arrives, you will acclimate faster than if you weren’t as fit. Thus, build your training base and aerobic fitness in the more temperate spring before your main season when you are riding harder and when the hot weather arrives.
When you acclimate, 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. Research shows that you can also adapt if you ride so that your core temperature rises 1 to 2C (1.8 to 3.6F) for a period of 60 to 90 minutes. The fitter you are, the faster you will acclimate.
Fortunately, you don’t have to train with a thermometer to acclimate! Simply ride hard enough to sweat heavily for 60 to 90 minutes. If you are already very fit, you can acclimate significantly 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.
If you live in an area where the summer isn’t hot, but you will be traveling to a hot place to ride, you can acclimate by riding with enough clothing so that you sweat heavily, which is particularly easy if you ride a trainer in the sun without a fan for cooling.
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 acclimate fully unless you spend a lot of time in a hot environment, i.e., acclimate passively.
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 acclimate 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
A 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.
Michael Glass’ Race Across AMerica.
Last week I reported on Glass’ RAAM and an interview with him. Unfortunately his neck problem that I noted in the column got significantly worse. Based on information from an MD on his crew and his crew chief I recommended that for safety reasons he drop out and Michael agreed. We’re all disappointed because he was riding well. However, he rode in eight days the same distance as the 2018 Tour de France – 2082 miles!
Of the 32 solo riders who started the race 16 DNFd. It’s a tough race!