Basics of Heat Training

 

Heat training is primarily used to gain heat adaptations, which improve performance for a hot race. In addition, heat training can be used to improve performance in cool to neutral conditions.  

 

Heat Adaptations 

When you do regular and repeated heat training, your body adapts so that it can cope better with heat stress.

The human body dissipates heat mainly through evaporation of sweat and through heat exchange between the skin and the air (called “convection”). With heat training, you can enhance your ability to dissipate heat. You will start to sweat earlier (ie, at a lower core temperature) and you will sweat more, which increases heat loss via sweat evaporation. Also, there will be an expansion of blood plasma volume and improved control of blood vessels in the skin, which increases blood flow to the skin for cooling via convection. 

These physiological adaptations will result in: 

Lower core temperature, Heat Strain Index, and heart rate for a given workout in given conditions. 

 

Heat adaptations can improve performance in cool-neutral conditions 

Heat training improves performance in hot and/or humid conditions, and can also improve performance in cool to neutral conditions. The plasma volume expansion seen with heat training increases total blood volume, which can enhance performance in any condition. 

In addition, scientific studies have shown that heat training has the potential to increase hemoglobin levels. However, for these adaptations, you'll likely need to perform a specific longer-term heat training protocol.

 

Basic heat training protocol 

To become fully heat adapted, you’ll need to complete 10–14 heat sessions within a 2–12-week timespan. Each session should include 45–80 minutes in Heat Zone 3, Heat Strain Index 3.0–6.9. (See the article CORE’s Heat Zones for more information) 

The quickest gains will come from heat training every day or every other day. Two to three sessions per week will build adaptations more gradually. (See the article Boosting Your Heat Adaptation Score for more information) 

 

Maintaining Adaptations 

Once you are adapted to the desired level, you can maintain those adaptations by performing 1–3 heat sessions per week. Failure to continue heat training will result in loss of adaptations. Adaptations decrease by about 2.5% for every day without heat training, disappearing entirely within 5–6 weeks.  

If several weeks pass without any heat sessions, adaptations can be regained simply by resuming heat training in a regular and repeated fashion. 

 

How To Do a Heat Session 

For specifics on how to heat train, please see the article How to do a Heat Session. 

 

 References 

Daanen HAM, Racinais S, Périard JD. Heat acclimation decay and re-induction: A systematic review and meta-analysis. Sports Med. 2018;48(2):409-430. https://doi.org/10.1007/s40279-017-0808-x.   

Oberholzer L, Siebenmann C, Mikkelsen CJ, Junge N, Piil JF, Morris NB, Goetze JP, Meinild Lundby AK, Nybo L, Lundby C. Hematological Adaptations to Prolonged Heat Acclimation in Endurance-Trained Males. Front Physiol. 2019;1;10:1379. https://doi.org/10.3389/fphys.2019.01379.   

Périard JD, Racinais S, Sawka MN. Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports. Scand J Med Sci Sports. 2015;25(1):20–38. https://doi.org/10.1111/sms.12408.  

Racinais S, Hosokawa Y, Akama T, et al. IOC consensus statement on recommendations and regulations for sport events in the heat. Br J Sports Med. 2023;57(1):8–25. https://doi.org/10.1136/bjsports-2022-105942.  

Rønnestad BR, Urianstad T, Hamarsland H, Hansen J, Nygaard H, Ellefsen S, Hammarström D, Lundby C. Heat Training Efficiently Increases and Maintains Hemoglobin Mass and Temperate Endurance Performance in Elite Cyclists. Med Sci Sports Exerc. 2022;54(9):1515-1526. https://doi.org/10.1249/MSS.0000000000002928. 

Taylor NAS. Human heat adaptation. Compr Physiol. 2014;4(1):325–65. https://doi.org/10.1002/cphy.c130022.