Heat Training for Sporting Performance

CORE allows you to monitor and record your core body temperature and the logical next question is, "how can these metrics be used?" This page is a resource for athletes and coaches which covers the training principles and includes guidance to help you get the most out of core body temperature metrics.  

This will also be a resource that we plan to update continuously and the best way to stay informed is to subscribe to our newsletter for sports performance.  

Page Content: 

  1. Sports Performance and Heat
  2. Heat Ramp Test
  3. Heat Block Training
  4. Heat Training to Maintain Performance
  5. Hot Baths and Saunas
  6. The Science of Heat Training
  7. Heat Training Dangers
  8. Feedback and Updates
  9. Resources and Studies

 

Safety Warning: The dangers of heat-stress are well documented and are also applicable to heat training. Before starting any heat training activity, please read our brief information on Heat Training Dangers and seek professional guidance.


Sports Performance and Heat 

Heat Training is a broad term to describe heat related athletic training and usually includes an initial Heat Block Training and subsequent Heat Training Workouts. Heat training is usually understood as being integrated into a complete training program (complementing interval, low intensity, high intensity, etc.).

Heat Training is aimed at conditioning the the body to become more efficient in cooling and increase the power output when the body heats.

Heat Training can be focussed on Heat Acclimation (Heat Adaption) which aims to improve athletic performance in hotter environments. It can also be undertaken with the aim of improving performance in mild and cool weather (and there are continuing debates among sports scientists regarding this). 

Here are further details in our Training Guide for Heat Training.

 

Heat Block Training is an intense period of (usually) two to four weeks to begin athletic Heat Training with a primary focus of stressing and conditioning the body (safely) by training in an elevated core body temperature zone. Heat Block Training is usually the start of the Heat Training program and when this is completed, athletes need to keep this 'topped up' with two to four Heat Training Workouts each week so that they don't loose the physiological benefits. 

 

Heat Acclimation / Adaption is Heat Training for the purpose of helping an athlete adapt / acclimatise to warm or hot weather competition. For example, European athletes from cool weather climates who are competing in the Kona Ironman in Hawaii or the Tour Down Under in Australia need to prepare their body to maintain the expected performance levels in the hotter and humid environments.  

 

Heat Training Workout is a single training session or activity which is part of the athletic training plan. Typically Heat Training Workouts are low intensity workouts and aim to maintain a steady core body temperature and heart rate while the power output will naturally decrease over time. 

 

Heat Training Zone is the core body temperature range which is optimal for Heat Training Workouts. If an athlete trains too low, they are not able to effectively gain the physiological benefits (described in more detail in the Science of Heat Training). Training too hot, about the Heat Training Zone can be counter-productive and even dangerous (more is not better). The Heat Training Zone can be determined with the Heat Ramp Test.

Core Body temperature Zones

 

CORE Threshold is an indicator of your own safe core body temperature upper-limit. This is useful to help 'think-ahead' and avoid heat-stress in training and competition. It is used to ensure that you train within your limits and can avoid fatigue, dangerous heat exposure and other consequences such as prolonged recovery.  

 

Heat Ramp Test 

This heat ramp test is in development and is focussed on an indoor trainer (bike). A heat ramp test for indoor treadmills is in development. 

Purpose of the Heat Ramp Test
• To define an optimal Heat Training Zone for Heat Training.
• A repeatable test to monitor changes in power output following Heat Training


Preparation

If there are any heart rate irregularities such as poor sleeping, the test should not be started. Consistency is important, for example coffee intake should not vary.

Important
After the initial ramp-up, when the test starts, focus on maintaining a constant heart rate. You will naturally need to gradually reduce your power output (to maintain the heart rate) and 
this is normal and correct.

Room and clothing
This test can be conducted on an indoor trainer in a heated environment or 'at home'. When the Heat Ramp Test is conducted in an unheated environment, overdressing is important and you can wear winter sportswear which helps contain the heat. Avoid using waterproof attire that completely traps sweat. 

Fans should not be used and draughts or airflow should be stopped as these can provide cooling. 

If your body is able to cool too much, this can cause the Heat Ramp Test to fail.


TIPS
This test can be very uncomfortable and generally, the warmer you dress to contain your heat, the shorter the test. Follow the safety guidance.

 

Heat Ramp Test Protocol

 1 - Slow Ramp-Up

Begin at 50% FTP and slowly increase to 80% FTP (target) over 20 minutes.

- 5 min 50% FTP
- 5 min 60% FTP
- 5 min 70% FTP
- 5 min 80% FTP
The timed ramp-up ensures the core body temperature rises slowly rather than rapidly.

Variations: The target FTP may be adjusted, if FTP is lowered this will extend the total test time. The target FTP should not be increased above 85% FTP.

If warm clothing is worn (to hold warmth), the target FTP should be lowered (e.g. 70%) and the total test time may be shorter. Before starting, be advised of potential risks of overheating and remain safe.

2 – First Checkpoint 38ºC / 100.4ºF

The moment core body temperature reaches 38ºC / 100.4ºF, take note of the Heart Rate and Power Output at this Checkpoint.
Heart Rate 1 _______________
Power Output 1 ______________

The test has now started, continue and maintain a constant Heart Rate and cadence.
You may reach the 38ºC / 100.4ºF checkpoint during Ramp-Up, before you reach the target FTP.

Or you may reach your target FTP and will need to maintain this until your reach 38ºC / 100.4ºF.

If you are struggling to reach 38ºC, you may be dressed too lightly or the room is too cool or breezy which is helping your body cool. In this case, the warmup and test time can be significantly longer and the test may fail if the core body temperature plateaus and stops rising.

When you start the test, to maintain the constant heart rate, you will generally need to gradually your lower power output.

3 – Second Checkpoint

Stop when:
a) your power output drops 20% below the Power Output 1 or;
b) when it becomes too difficult to pedal or you feel unwell

Core Body Temperature 1  ________________

The Test is now complete. Stop all activity completely and take note of the core body temperature.

Rest, but don’t use fans or extra cooling

4 – Stop

Take note of the highest core body temperature.
Core Body Temperature 2 ________________

As you rest, your core body temperature can continue to rise and peak before cooling.

Heat Ramp Test Core Body Temperature

Graph 1.0 with an example Heat Ramp Test on an indoor bike trainer and winter clothing to elevate temperature

On the Graph please note Heart Rate (bpm) remains constant during the test

 

Heat Ramp Test Key Points

The Heat Training Zone is calculated from the Core Body Temperature 1 which was measured at the second checkpoint. 

Celcius: Core Body Temperature 1 minus 0.5ºC to minus 0.3ºC
In this example the Heat Training Zone is 38.4ºC to 38.6ºC
Fahrenheit: Core Body Temperature 1 minus 0.9ºF to minus 0.5ºF    
In this example the Heat Training Zone is 101.1ºF to 101.5.ºF


Within this Heat Training Zone, the athlete endures enough ‘stress’ for this be beneficial for heat training (to prompt an increase in blood plasma) but retains a sufficient buffer against risks and detrimental impact.

After Heat Block Training (and assumed improved heat adaption / efficiency) it would be expected that repeating the Heat Ramp Test would show:

  • It takes longer for the athlete to reach 38ºC
  • With the same effort, the test takes longer until the athlete reaches Core Body Temperature 1
  • The athlete will maintain a higher comparable power output (and slower drop) during the test 

 

 

Heat Block Training (2 – 4 weeks) 

Heat Block Training precedes Heat Training and intensively builds your athletic conditioning before you move into your regular training program. The underlying benefit of Heat Block Training is increased power output and more efficient cooling. 

Coaching approaches can vary significantly, for example, Heat Block Training can be started early in the training program or later in the program, shortly before competition. Often an early start at the beginning of the training season is favoured as a routine is established with minimal disruption to other training components before major competitions. 

Heat Block Training

Your core body temperature behaviour and your physical condition is very individual to you so the following information is intended as a general guide which should be adapted by your coach to ensure it is suits your objectives and enables you to remain safe. Be aware that people without sports training are advised to seek professional guidance first.

A typical Heat Block Training period of 2 - 4 weeks involves 6 - 7 Heat Training Workouts a week and can also be combined with other training workouts (typically low-intensity workouts).

 
Training Setup 

This is an indoor activity undertaken for the duration of two to four weeks using a home trainer. Preferably, it is a warmer room and artificially increasing your heat by overdressing with leg warmers and a jacket which contains your heat, will make it easier. Consistency is important so ensure that the clothing, setup and room temperature doesn’t change for the duration of the Heat Block Training.  

The Heat Training Workout (6 - 7 times per week)

With the Heat Ramp Test, you should already have identified your individual Heat Training Zone. For many athletes this may be around 38.5ºC / 101.3ºF. 

To reach your Heat Training Zone requires a good physical effort though this zone is well below your Core Threshold. Your coach can provide further guidance if you should to adjust Heat Training Zone.  

During the workout, as you get close to the Heat Training Zone, begin to back-off your effort. As core body temperature is a slow-moving metric, you can plan ahead to try and stabilise. A typical workout duration is 45 - 60 minutes within the Heat Training Zone and total activity duration of 90 minutes maximum.
 
You may notice that your power output is far lower than you anticipate. This is normal and take care not to follow be guided by power output. If your ‘set point’ is 38.5ºC, aim to regulate your effort to keep your core body temperature between 38.3ºC and 38.7ºC (100.9ºF - 101.7ºF).  
 
Your heart rate will typically be within your threshold heart rate range and can be used as an indicator to help you naturally adjust and regulate your power to try and remain close within your Heat Training Zone.  

Benefits 

Usually after just a few days of Heat Block Training, athletes will start to see results in which they can maintain the Heat Training Zone core body temperature, but will see an increase in their power output levels.

An independent test of cyclists published by John Hughes on Road Bike Rider reported a 6-8% improvement among riders who undertook heat training against a control group.

Heat Training to Maintain Performance 

After Heat Block Training, the objective is to maintain the conditioning you have acquired in preparation for competition, while also doing all of your other training activities such as Interval Training, High and Low Intensity Training, Strength Training, Outdoor and Endurance Training. Typically 2 - 4 Heat Training Workouts are incorporated into the weekly training schedule and these can be combined with other workouts (e.g extending a HIIT workout so that it transforms into a Heat Training Workout).

Heat Training Workouts

 

Due to the individuality of athletes and the many different training approaches, this introduces a huge scope for conducting effective Heat Training and so the following guidance is published with the understanding that it should be adjusted to suit.

Heat Training Guidance 

A single Heat Training Workout can be planned on a lower intensity day. With this approach, as a rough guide, the training program would include 2 - 4 Heat Training Workouts each week.  
 
Alternatively, a high intensity workout can be planned to elevate the core body temperature into the Heat Training Zone. To compensate for the elevated temperature, the power output needs to be reduced. This means some existing training workouts can be modified or extended for the heat training value. 
 
Some important things to notes on this approach: 
  • Continually monitor the core body temperature to avoid exceeding your CORE threshold. 
  • For Heat Training Workouts, Power Output / Intensity should be decreased. If the intensity is usually set at 80% FTP, this is adjusted down to between 50 and 60% of FTP. 
  • Monitor heart rate and core body temperature to gauge effort and recovery
  • During efforts, fans may be necessary. The workout can be be started without fans and once the Heat Training Zone is reached, the fans are turned on.
  • Recovery time between intervals may need to be increased, the durations of the intervals may need to be decreased
  • Seek to maintain an elevated core body temperature after the session and avoid cooling down rapidly after the workout.  

Hot Baths and Saunas 

Using Hot Baths and Saunas can help increase the core body temperature or to maintain core body temperature and slow the rate of cooling.  
 
Maintaining the elevated core body temperature directly after training can have the effect of prolonging the physiological effects of conditioning the body while saving physical effort.  
 
As a guide, athletes should avoid rapid cooling following training, particularly for Heat Training. At minimum, sit and allow the body to slowly cool and return to their normal temperature.  
 
Warning: Please take note of the risks of Heat Training and seek guidance from an accredited and experienced coach.   

The Science of Heat Training

Why does Heat Training help improve athletic performance? The short answer is that this stress acts to condition the body.   
 
During intense sports, as the body heats, the body expends more energy pumping blood to the skin to aid cooling. This means there is less blood directed to the muscles for power generation. By default, when you are cooler your effective power output is higher. 
 
The body has a mechanism to increase the level of blood plasma when body temperature reaches around 38.5ºC / 101.3ºF to help with the delivery of the oxygen carrying hemoglobin in the red blood cells to the tissues. 
 
However, this increase in blood plasma reduces the hematocrit which is the percentage of red blood cells to plasma. The body naturally seeks to balance this by then producing more red blood cells.

The result, a higher blood volume and the body has more blood to work with. This means more oxygen in the hemoglobin carrying red blood cells can reach the muscles. The muscles are not as starved because they are receiving more oxygen, so the power output is higher. But also, the increased blood volume makes the body more efficient in cooling.

Heat Training Dangers 

Heat Training is not particularly complicated; you just need an indoor trainer, you follow a set plan and watch your core body temperature. And it can deliver measurable performance benefits within weeks, however you need to listen to your body to do it safely and effectively.

Heat Training sessions, even at very low power, put your body in stress and can feel very uncomfortable. These can be some of the hardest, low-power, slowest training sessions you ever do.

If you are feeling unwell, stop and immediately cool yourself. Do not over-do Heat Training and continuously monitor your core body temperature. There is a risk of danger because elevated temperatures introduce heat-stress and can result in blowing-up (which is the complete loss of power), collapsing and a short or long-term impact on your recovery and performance. 

This type of training should be planned and executed with professional guidance from an accredited and experienced coach. If you are uncertain whether you can perform Heat Training, consult your doctor first.

The CORE Body Temperature monitor is not a medical device and you are advised to read the disclaimer before using it. 


Feedback and Updates

Do you feel something is missing? Can you share additional information or Heat Training approaches that need to be reflected on this page? Simply let us know as this is intended to be a curated page that is updated and optimised. 

The easiest approach is with the chat/dialogue function (green button on the bottom right). If you would like us to contact you, please include your details.

 

 

Resources and Studies

Heat Training Resources

TrainerRoad: How to Get Faster with Heat Training - Jonathan Lee 2017 July

TrainingPeaks: Effective Strategies to Beat Summer Heat - Embracing heat training can give you some powerful adaptations - William Ritter 2020 August

Kenefick RW, Ely BR, Cheuvront SN, Palombo LJ, Goodman DA, Sawka MN. Prior heat stress: effect on subsequent 15-min time trial performance in the heat. Med Sci Sports Exerc. 2009 Jun;41(6):1311-6. doi: 10.1249/MSS.0b013e3181988c14. PMID: 19461533.


Heat Acclimation Resources

Garrett AT, Creasy R, Rehrer NJ, Patterson MJ, Cotter JD. Effectiveness of short-term heat acclimation for highly trained athletes. Eur J Appl Physiol. 2012 May;112(5):1827-37. doi: 10.1007/s00421-011-2153-3. Epub 2011 Sep 14. PMID: 21915701.

Heathcote SL, Hassmén P, Zhou S, Stevens CJ. Passive Heating: Reviewing Practical Heat Acclimation Strategies for Endurance Athletes. Front Physiol. 2018 Dec 20;9:1851. doi: 10.3389/fphys.2018.01851. PMID: 30618849; PMCID: PMC6306444.

Stanley, J., Halliday, A., D’Auria, S. et al. Effect of sauna-based heat acclimation on plasma volume and heart rate variabilityEur J Appl Physiol 115, 785–794 (2015). https://doi.org/10.1007/s00421-014-3060-1

Scoon GS, Hopkins WG, Mayhew S, Cotter JD. Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. J Sci Med Sport. 2007 Aug;10(4):259-62. doi: 10.1016/j.jsams.2006.06.009. Epub 2006 Jul 31. PMID: 16877041.


Sports Science Resources

** Périard, J.D.,& Racinais, S., 
Heat Stress in Sport and Exercise : Thermophysiology of Health and Performance
Springer, 2019, DOI: 10.1007/978-3-319-93515-7

Luetkemeier MJ, Thomas EL. Hypervolemia and cycling time trial performance. Med Sci Sports Exerc. 1994 Apr;26(4):503-9. PMID: 7515456. 

Lorenzo S, Halliwill JR, Sawka MN, Minson CT. Heat acclimation improves exercise performance. J Appl Physiol (1985). 2010 Oct;109(4):1140-7. doi: 10.1152/japplphysiol.00495.2010. Epub 2010 Aug 19. PMID: 20724560; PMCID: PMC2963322.

Baranauskas, Marissa N.1; Constantini, Keren2; Paris, Hunter L.3; Wiggins, Chad C.4; Schlader, Zachary J.1; Chapman, Robert F.1 Heat Versus Altitude Training for Endurance Performance at Sea Level, Exercise and Sport Sciences Reviews: January 2021 - Volume 49 - Issue 1 - p 50-58
doi: 10.1249/JES.0000000000000238

Oberholzer L, Siebenmann C, Mikkelsen CJ, Junge N, Piil JF, Morris NB, Goetze JP, Meinild Lundby A-K, Nybo L and Lundby C (2019) Hematological Adaptations to Prolonged Heat Acclimation in Endurance-Trained MalesFront. Physiol. 10:1379. doi: 10.3389/fphys.2019.01379