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

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 a precursor to Heat Training and is an intense period of one to two weeks with a primary focus of stressing and conditioning your body (safely) in order to increase your physical performance in competition.  

Heat Training maintains the physical benefits from Heat Block Training and is integrated into the training program (complementing interval, low intensity, high intensity, etc.) 

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

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

Provisional Heat Ramp Test 

NOTE: The following test is a provisional test which is currently in testing.
Your CORE Threshold is a specific temperature, individual to you, which is a safe limit. This can be determined with a short test and the temperature value can then be used as a guide for training and for competition to ensure that you avoid heat-stress and resulting consequences. 

The CORE Threshold is a temperature value that can also change, depending on your condition, so the test can be repeated every few months (or when needed) and help you make any adjustments for further Heat Block Training and Heat Training.  

As with many performance tests, there are varying methods (which can also deliver varying results). We are introducing one approach and welcome input from coaches and sports scientists. 

 
Method: CORE Threshold – Heat Ramp Test 

This provisional method has been developed by CORE based on the expertise from leading sports coaches. 
 
TEST 
  1. Start a steady state workout - a cardio workout intended to maintain a continuous, steady effort. Don’t use fans or any other cooling.  
  2. Monitor you live core body temperature as it rises until the rate of change begins to decrease and the temperature flattens.   
  3. Maintain this temperature for 15 minutes.  

 
RESULT 
Your last maximum temperature you record will roughly be your CORE Threshold.

NOTES
Across different sports, the activity and approach can change. Although core body temperature metrics are the orientation point, it may be useful to use other metrics as guidance. As an example, in cycling FTP levels can be set as markers. This page will be updated to optimisation current methods and to include alternative methods for Heat Ramp Tests.

 

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 or even a plastic painter's suit, 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

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.