CORE's Heat Adaptation Score

Disclaimer: Heat Adaptation requires stressing the body's thermoregulatory system. All information below is meant as general guidance. Please consult a medical professional and coach before undertaking any heat training. If at any point you experience any symptoms of heat-related illness, stop immediately and consult a medical professional.

Are you ready to perform your best in hot conditions? CORE's Heat Adaptation Score lets you track your heat adaptation progress to see how much of your potential you’ve reached. The score indicates how adapted you are to the heat, on a scale from 0 to 100%. The Heat Adaptation Score uses an evidence-based formula, derived from extensive independent scientific research and refined in CORE's own research lab.

It is well-known that frequent exposure to heat strain induces heat adaptations. Therefore, the Heat Adaptation Score is based on the heat strain accumulated during your daily training sessions. This heat strain is measured by CORE’s Heat Training Load, which ranges from 0 to 10 each day. The Heat Training Load is calculated based on how much time you’ve spent with an elevated Heat Strain Index (Heat Zones 2 & 3).

On days with an adequate Heat Training Load, your Heat Adaptation Score will increase. The higher the load, the larger the heat adaptation benefits. A couple of days with no Heat Training Load will cause your score to decline. 

Levels of Heat Adaptation

There are four levels of heat adaptation:

0–24%: Thermal Rookie

Your heat adaptation level is low. During exercise in warm conditions, you may feel uncomfortable and experience a performance decline. Be careful during training and competition in the heat and take strong cooling measures. Perform heat training sessions more frequently to increase your Heat Adaptation Score.

25–49%: Heat Accustomed

You know how it feels to exercise under heat strain and your body may have developed some physiological adaptations. This will help your performance in warm weather, but you still need more heat training sessions to better adapt to hot conditions.

50–89%: Heat Adapted

Your body has gained substantial heat adaptations and you have the potential to perform very well at hot races. Strategic cooling and pacing are still important, but you’ll have a substantial advantage over competitors who are not heat adapted. Keep striving to reach the top of this range!

90–100%: Heat Champion

Your heat adaptation level is very high: you have unlocked your performance potential! The adaptations you have gained will optimise your endurance performance in both hot and cool conditions. Keep doing 1–2 heat training sessions a week to maintain your adaptation level.

Boosting the Heat Adaptation Score

Disclaimer: the following are examples of different heat training scenarios with corresponding adaptations meant for illustrative purposes. Please consult a medical professional before undertaking heat training.

Exercising for 45–75 minutes in Heat Zone 3 (Heat Strain Index 3.0–6.9) gives the most effective heat training. This will yield a Heat Training Load of 6–10.

Achieving Heat Training Loads of 9–10 for 5–6 days a week will raise the Heat Adaptation Score to 85–95% within 2 weeks.

Less frequent Heat Training Loads of 5–6 over a span of 12 weeks. will slowly raise the Heat Adaptation Score to a similar level.

Once you’re well heat adapted, you can maintain your score with 1-2 heat training sessions per week.

For additional scenarios, please see the article Boosting your Heat Adaptation Score.

For examples of workouts yielding various Heat Training Loads, see the article Examples of Heat Training Loads.

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.

Esh, CJ, Carter, S, Galan-Lopez, N. et al. A Review of Elite Athlete Evidence-Based Knowledge and Preparation for Competing in the Heat. J Sci Sport Exerc. 2024. https://doi.org/10.1007/s42978-024-00283-y

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.

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