Heat Training for Sporting Performance

The heat ramp test was an early way of identifying each individual's core temperature range best suited for heat training. It has been replaced with Heat Zones that better predict heat adaptation. Also, please see the article Individuality of Heat Zones.

Heat Ramp Test

This heat ramp test is in ongoing development and is suited for the indoor trainer (bike). A heat ramp test for indoor treadmills is available on this page.

Purpose of the Heat Ramp Test
• To identify 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 slow ramp-up, during the test, focus on maintaining a constant heart rate. It is expected that you will naturally need to gradually reduce your power output to compensate in order to maintain a steady heart rate and this intended and correct.

Room and clothing
This test can be conducted on an indoor trainer in a heat chamber or at home in an unheated environment.

When the Heat Ramp Test is conducted in an unheated environment, overdressing is important, wearing winter sportswear helps contain the heat.

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. For 'at home' tests without a warmed environment, the warmer you dress to contain your heat, the shorter the test.

For further information, we have a supplement for the Heat Ramp Test for cyclists and a suplement for the Heat Ramp for runners which are worth reading in advance to ensure you get the best out of your test.

Heat Ramp Test Protocol

Step 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.

The warmup can be adapted to suit, but should be consistent for repeatability and be advised of potential risks of overheating and remain safe.

Step 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 and 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.

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

If you are struggling to reach the first checkpoint, this could be related to your setup or your own individual thermoregulation and further information is available here.

Step 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.

Note your 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

Step 4 – Stop

Take note of the highest core body temperature.

Note your Core Body Temperature 2 ________________

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

Example of a successful Heat Ramp Test

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

Notes:

On the Graph please note Heart Rate (bpm) remains constant during the test.
The Core Body Temperature 2 value is not used for calculation and this value does not indicate heat threshold so this value is solely being documented and not applied.

Calculating the Heat Training Zone

The Heat Training Zone (range) is calculated from the Core Body Temperature 1 value.

Celcius calculation	Fahrenheit calculation
Core Body Temperature 1 minus 0.5ºC to minus 0.3ºC = Heat Training Zone In the Heat Ramp Test example above the Core Body Temperature 1 is 38.9ºC so the Heat Training Zone is 38.4ºC to 38.6ºC	Core Body Temperature 1 minus 0.9ºF to minus 0.5ºF = Heat Training Zone In the Heat Ramp Test example above the Core Body Temperature 1 is 102.0ºC so the Heat Training Zone is 101.1ºF to 101.5.ºF

Within the Heat Training Zone, an 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.

Heat Training Zone

The temperature range for the Heat Training Zone may be lower than anticipated. In contrast to other sports training workout, for Heat Training "More is not better". Going beyond the heat training zone will not increase the benefits.

Repeating the Heat Ramp Test after Heat training

After Heat Block Training (and assumed improved heat adaption / conditioning) 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 in power) during the test .

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.

To learn more about the Science of Heat Training, check our collated collection of the most relevant thermal regulation and sport performance research papers.

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.

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 variability. Eur 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 Males. Front. Physiol. 10:1379. doi: 10.3389/fphys.2019.01379