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 

CORE Threshold is an indicator of your personal limit core body temperature limit which acts as a guide to define your safe limit. This is useful to help avoid heat-stress in competition and to ensure that you train within your limits to avoid negative consequences and prolonged recovery.  

Heat Block Training is an intense period of one to two weeks with a primary focus of stressing and conditioning your body (safely) by training in a higher core body temperature zone in order to increase your physical performance in competition. This needs to be followed by 'topping-up' heat exposure (during regular training) so that the physiological benefits are not lost. 

Heat Acclimation / Adaption training is designed to help 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 Acclimation / Adaption is not the focus of this resource though is worth introducing as some athletes automatically consider this to be Heat Training.

Heat Training includes the physical benefits from Heat Block Training and is integrated into the complete training program (complementing interval, low intensity, high intensity, etc.) As opposed to Heat Acclimation / Adaption which aims to improve athletic performance in hotter environments, Heat Training is aimed at conditioning the the body to become more efficient and improvement performance in mild and cool weather competition.

The good news for athletes is that it takes just a few weeks of Heat Training to yield measurable performance improvements. 

 

Heat Ramp Test 

This heat ramp test is in development

Purpose of the Heat Ramp Test
• To define an optimal Heat Training Zone for Heat Block Training, Heat Training and Heat Adaption Training
• To be a repeatable test in which changes in power output can be identified

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.

Room setup
Overdressing is important.
Warm enclosed room with no fans or draught

TIP - This test can be very uncomfortable, while taking all safety precautions, the warmer you dress to contain your heat, the faster the test. 

TIP - If you are dressed too lightly or have cooling with a fan or a draught, then this test can fail and your core body temperature will stabilise and stop increasing.

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 (1 – 2 weeks) 

Heat Block Training precedes Heat Training and intensively builds your athletics conditioning before you move into your regular training program in which Heat Training is incorporated to help you maintain your condition. The underlying benefit of Heat Block Training is increased power output. 

Coaching approaches can vary significantly for Heat Training, for example, Heat Block Training can be started early in the training program or later in the program, shortly before competition.  

As core body temperature and your physical condition is individual to you, this is a general guide to Heat Block Training and should be adapted by your coach to ensure it is designed to suit your objectives and enable you to remain safe. Be aware that people without conditioning and sports training are advised to seek professional guidance and lower their temperature limits to avoid risks. 

 
Training Setup 

This is an indoor activity undertaken for the duration of one to two 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.  

Start Heat Block Training 

Define a ‘set point’ core body temperature, this is generally around 38.5ºC / 101.3ºF and requires a good physical effort though is below your CORE Threshold. Your coach can provide further guidance if you need to adjust the ‘set point' temperature.  

During the activity, as you get close to the ‘set point’, begin to back-off your effort. As core body temperature is a slower moving metric, you can plan ahead to try and stabilise. A typical activity duration is 60 minutes within the ‘set point’ with total activity duration of 90 minutes.   
 
You may notice that your power output is far lower than you anticipate. This is normal though take care to avoid orientating to heart rate or power output levels. 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 to your ‘set point’.  

Benefits 

Usually after just a few days of Heat Block Training, athletes will start to see results in which they maintain the ‘set point’ 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 

Heat Training should follow Heat Block Training and the objective is to maintain the conditioning you have acquired in preparation for competition while also completing all of your other training activities such as Interval Training, High and Low Intensity Training, Outdoor and Endurance Training.  

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

Heat Training Guidance 

To maintain condition, a single Heat Block Training effort can be planned on a lower intensity day. With this approach, as a rough guide, the training program would include one Heat Block Training effort each week.  
 
Alternative, a high intensity workout can be planned to raise the core body temperature and maintain this elevation. To compensate for the elevated temperature, the power output needs to be reduced. 
 
Some important things to notes on this approach: 
  • Only begin this after a successful Heat Block Training session has been completed
  • Carefully monitor the core body temperature to avoid exceeding your CORE threshold. 
  • Intensity should be decreased. If the intensity originally set at 80% FTP, this needs to be 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
  • 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 immediately after the session.  

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, to maintain the advantages of Heat Training, athletes should avoid rapid cooling following training. At minimum, sit and allow the body to slowly cool and return to their normal temperature.  
 
Warning: Please take note of the dangers of Heat Training to avoid the risks 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