Endurance athletes are flocking to saunas and sweating away on indoor trainers to try to gain the latest edge on their competitors.

Done right, the benefits of heat training can be dramatic. Riding in a 30-plus-degree chamber with his core temperature above 38.5 degrees, one of our male riders was able to push 330 watts for almost half an hour longer than his baseline after he had completed a controlled block of heat training. Being able to handle heat better makes racing in extreme temperatures much safer. Heat training also benefits athletes’ performances no matter the temperature, as it stimulates increases in blood plasma volume, in much the same way that altitude training does, so your body can better provide your muscles with oxygen. To get the benefits of heat training, you have to do it properly though.

EF Pro Cycling Head Doctor Jon Greenwell designed the heat training protocol that our athletes use to prepare for races like the Tour de France and Vuelta a España. He is ready to share our secrets with you, so you can carry out your own blocks of heat training safely and effectively.

Benefit from the knowledge and experience our team has earned in the WorldTour. Whatever your ambitions, Team EF Coaching is ready to teach you Tour de France-proven training, nutrition, and technique to make you a better cyclist.

Your body adapts to heat in a number of ways. You start sweating sooner. You start sweating at lower temperatures. And you lose more fluid, which is a good thing, as it allows you to regulate your body’s temperature better. The sodium concentration in your sweat also decreases, so you lose less sodium, which helps prevent cramps. Heat training also leads to increases in blood plasma volume, which helps your heart transport oxygen to your muscles more effectively. Heat training helps your body to regulate your heart rate during intense efforts in high temperature as well.

“If you're not acclimatized, one of the ceilings of performance is that your heart rate drifts up and up and that's not good,” Doctor Greenwell says. “Eventually, the ceiling you hit is your maximum heart rate rather than your maximum power output. But we know that when you're acclimatized, that heart-rate drift is way better and for a given power output, your heart rate will be lower.”

Testing that Doctor Greenwell has done with our athletes in the lab at Loughborough University proves just how effective heat training can be.

“We have got really good data within the team that shows how well the riders acclimatize,” Doctor Greenwell says. “If your core temperature and the outside temperature are hot, you can maintain a given power output for a much longer period of time if you have done a block of heat training. We've got data from some of the riders on our team after we put them in a heat chamber in a really controlled environment and ran tests in extreme temperatures. And the improvements after a block of heat training are profound. If you are climbing the Alpe d'Huez or the Galibier on a standard day in the summer, it can get you 20 minutes further up the climb before the heat really gets to you.”

The key to heat training is to keep your core body temperature over 38.5 degrees celsius for close to an hour. You don’t want to see it go higher than 39 degrees celsius, as you will then start to suffer harmful consequences.

“You don’t want to go much above 39 degrees centigrade,” Doctor Greenwell says. “We know once you start hitting 40 or 41 degrees centigrade, that's when you will experience the negative effects. Our body's enzymes only work in a fairly narrow temperature range. So, if you're getting much hotter than that, you're going to get detrimental effects. Try keep in a temperature range between 39 and 40 degrees.”

Our riders do two types of heat training: active and passive. Passive heat training involves sitting in a hot bath for close to an hour. Riders usually do this immediately after a training session.

“When you are in there, you want to try to keep yourself completely submerged, so only your head is sticking out,” Doctor Greenwell says. “Then, you just sit there and monitor it.”

A hot bath is more effective than a sauna, since it is easier to control the temperature by adding more hot water. Passive heat training is less stressful overall than active heat training, which means you can train harder on the road.

Active heat training involves riding indoors on a Wahoo KICKR in winter gear, checking your core temperature every five minutes to make sure you remain within the appropriate range.

“Once you get up to temperature, you want to try and maintain that temperature for between 50 minutes to an hour to get that adaptation,” Doctor Greenwell says. “The riders will be inside with leg warmers, waterproof jacket, thermal base layer, gloves, and a bobble hat on and then training inside, but we ask them to check their temperature regularly. That way we know A, they're training hard enough, but also B, that they're not running into the risk of overheating and then causing themselves any problems. We do it really carefully.”

The benefit of an active session is that it better simulates the stress of racing in extreme heat. The downside is that it is harder than passive training, so your overall training plan needs to take that into account. Note that these sessions should be focused on maintaining temperature, not pushing maximum power, so dress up and get ready to sweat.

Heat training needs to fit into your overall training and racing schedule. It is fatiguing and will compromise the training that you are able to do on the road. Doctor Greenwell recommends reducing your overall training volume by 20 percent during a heat training block in order to account for the additional stress.

Timing your heat training blocks is also crucial. You want to retain the benefits of the sessions for race day and still be able to do the best possible on-bike training during the days and weeks leading up to your key event.

Research shows that athletes will maintain adaptations from a block of heat training for up to four weeks. In order to get those benefits, athletes first need to do a concerted block lasting seven to 14 days, depending on their individual physiology and how responsive they are to the heat stimulus. Those blocks can be very fatiguing, both physiologically and psychologically. To reduce the load, Doctor Greenwell recommends that athletes mix active and passive sessions.

The scientific literature also shows that athletes who have done an initial seven- to 14-day block can regain those adaptations if they later complete shorter three- or four-day blocks to ´top-up´ their gains.

That is why our riders will often complete an initial extended block of heat training about five weeks out from their key event. As their key race approaches, they will then complete a second, shorter block of three or four days, which is much less fatiguing than a longer block. This allows them to regain all of the adaptations from their earlier heat training without compromising the work they want to do on the bike during the crucial weeks before the race.

To be safe, our riders measure their core temperatures using a medical grade thermometer pressed into their ears every five minutes. If they are in the lab, they will use a swallowable thermometer pill. Both methods are more accurate than algorithm-driven devices that estimate core temperature based off of skin temperature.

Drinking enough fluid during both active and passive heat training sessions is crucial. You do not want to get dehydrated. Weigh yourself before and after each session and try to finish with the same amount of fluid with which you started. Doctor Greenwell recommends beginning each session with at least two full bottles at hand.

There is no point doing a shorter heat session. You really do need to keep your temperature up for close to an hour to get the adaptations you are looking for. And your temperature needs to be above 38.5 degrees to benefit at all from the session.

If you are taking any prescription medications, consult the doctor who prescribed them before starting heat training. Heat training also puts a considerable amount of stress on your heart so consult your doctor if you have a history of cardiac problems.

Every athlete will respond to heat training differently, so make sure to consult closely with your coach so you can adapt your workload accordingly.

Benefit from the knowledge and experience our team has earned in the WorldTour. Whatever your ambitions, Team EF Coaching is ready to teach you Tour de France-proven training, nutrition, and technique to make you a better cyclist.