Over the past few years, indoor bike training and racing has exploded in popularity. For some athletes, it's a fallback during cold weather. For others, it's a passion in itself. But all indoor cyclists face one huge hurdle – underperformance caused by overheating.  

 When core body temperature rises above an ideal range, cyclists' power decreases. During an indoor race, this underperformance can make the difference between a podium spot and floating around in the virtual pack. The key to success is training hot and racing cool. 

Most indoor bike racers have some strategies to stay cool. They start with a fan. Then add a second fan. Windows are opened. A bigger fan is found. And finally they move to the garage (with the garage door open). But the buckets of sweat continue, and their power continues to drop as their core body temperature continues to rise.  

During indoor racing, cooling both the room and your body is important. But also important is training your body to deal with the heat. Heat training allows cyclists to generate power to their full potential, even in warmer temperatures. Heat training can also help increase or maintain higher blood plasma levels, which will also help increase hemoglobin levels (like altitude training does). A bike trainer, together with CORE, makes heat training simple.  

CORE provides a number of resources on how to safely and effectively heat train. If you're new to heat training, start with that information to learn the basics. This post focuses on indoor bike training & racing and the specific strategies useful for that sport.

Heat training starts by identifying your heat training zones. This is done through a heat ramp test, described in detail here.  

Once you know your ideal heat training zone, doing heat training a minimum of 2 or 3 times a week will adapt your body to the heat. During each session, maintain your core body temperature in your heat training zone for approximately 45 to 75 minutes (consult your coach for your individual needs). Note that each training session will be longer than that, as it will take some time to elevate your core temp into your heat training zone. 

Let's say you've identified your optimal heat training zone as between 38.4ºC and 38.6ºC. You can reach that core body temperature in a number of ways – a warm room, extra clothes, or higher intensity (or any combination of the three). Do not use fans – they simply prolong the time it takes to reach the heat training zone. 

Note that core body temperature is a slow-moving number. Its rise will lag behind an increased heart rate, and lag even further behind an increase in power. You'll quickly learn how to “ease into” your heat training zone and stabilise your core temperature with small adjustments to power and heart rate. 

Most cyclists are accustomed to varying intensity to reach various heart rate or power targets. However, during heat training, you will vary intensity to maintain a targeted core body temperature. Staying in your heat training zone is the primary goal, and heart rate and power are secondary. 

At first, you will notice that your power is much lower than typical for a given heart rate. This is to be expected, as your body is diverting blood from muscles to cool itself. After just a few days of heat training, you will start to see your power numbers increase again. This is the result of your body adapting to the heat training. 

Set-up: cycling jacket, long pants, warm room, no fan

1. Warm-up at moderate intensity until your core body temp is close to your heat training zone. If it's difficult to reach the heat training zone at the desired intensity, add clothes or warm up the room. 
2. Monitor your heart rate and power to ease into the heat training zone. Keep your core body temp in that zone for 45 to 75 minutes. Adjust heart rate and power as needed to stabilise your core temperature. 
3. Optionally, after the workout is completed, go into the sauna or hot bath to maintain your core body temperature in the heat training zone. This “time in zone” counts toward the time needed to adapt to heat. 
   
   Another way to reach the heat training zone in low ambient temperatures or with a very easy effort is to use a CORE full-body indoor heat training suit. This ‘portable environmental chamber’ traps all moisture next to the body, meaning that the body cannot cool itself through sweat evaporation. This will cause the core temperature to rise quite quickly even at a low effort. Please follow the safety advice prior to any type of heat training.
   

Playing it safe

Heat training can help protect you from heat stress. But certain precautions are needed to do it safely.

It is important to not exceed your identified heat training zone. Reaching a higher core body temp (zone 5, the heat stress zone) is not beneficial and there is no additional training advantage to training hotter than needed. This can causes too much stress and fatigue, can result in illness, and can be dangerous.

Also, do not heat train when…

...feeling ill or off. Listen to your body!
…doing strength training
…pregnant.

Follow safety advice

Prior to any form of heat training, seek professional medical advice and it is recommended to follow guidance from an experienced coach.

Set-up: cycling shorts, normal room temperature, fan available (but begin with it off)

1. Do your high-intensity workout as normal while monitoring your core body temperature. If necessary, use the fan or other cooling measures to ensure you do not reach the heat stress zone. 
2. After finishing the high intensity portion of the workout, turn off the fan. Ride at an intensity that will keep your core temp in the heat training zone.  
3. End the workout after you have accumulated 45 to 75 minutes total in the heat training zone. 
4. Optionally, after the workout is completed, go into the sauna or hot bath to maintain your core body temperature in the heat training zone. 

Set-up: shorts, cool room, fan

1. Strength training is best done with a core body temp below the heat training zone. In other words, do not use strength training to accumulate heat training time. 
2. Monitor core body temp throughout the workout.
3. For maximal effect, cool off between sets to stay below heat training zone. 

After a couple of weeks of heat training, most athletes will show less power drop with increased core temperature. This means they can give a stronger performance when racing or doing high intensity workouts. 

Even so, indoor racers will still want to cool themselves and their surroundings as much as possible. The key points are cool room temperatures, lots of air flow, and evaporating water from the skin. Creative solutions abound, but here are some proven measures for cool indoor racing: 

• bring in more and bigger fans
• cool the room before starting
• open windows to allow air exchange with the outdoors. Fans are not as effective if they're simply recirculating warm air.
• strategically place cold, wet towels on your body 
• regularly mist water onto your body with a spray bottle 
• pre-chill your drinks 
• try an ice vest 
• and did we mention more fans?

Throughout the race, monitor your core body temp. You can use this information to either slow your pace (to avoid the heat stress zone, which will majorly and involuntarily slow your pace) or to take additional cooling measures, or implement hydration strategies.

Training hot and racing cool: this means you're increasing the temperature range in which you can effectively perform; and on race day you're keeping your core body temperature in your ideal performance range. These two strategies will help you unleash your full potential throughout the exciting indoor race season.