If you have an early season race and/or will be racing in a climate that is significantly warmer than the climate in which you train, acclimating to that hot environment prior to race day is a key factor in success.
Why Do You Need to Acclimate to the Heat?
For every 10 degrees above 60º F, your run pace decreases by 10-30 seconds per mile, and temps above 80º F negatively impact your FTP – these effects can be lessened by acclimating to higher temperatures.
Physiologically, when your core temp rises, your brain cannot recruit muscles as well, or as intensely as it does at cooler temps. Skin blood flow increases dramatically in the heat to try to cool down your skin – your largest organ, which diverts blood away from the muscles. Heat also impacts cognitive functioning, your perception of effort, and therefore your motivation and willingness to exercise hard.
An acclimatized athlete will have a lower heart rate, lower core temp, and lower skin temperatures (greater circulatory stability) than someone who is not acclimatized.
What Adaptations Occur During Heat Acclimatization?
- Expansion of blood plasma volume, which leads to a decreased heart rate
- Enhanced cardiovascular stability
- Improved sweating as a cooling mechanism, so you start sweating earlier
- Improved skin blood blow
- Better fluid/electrolyte balance as your body learns to conserve and re-absorb electrolytes
- Improved thermal tolerance, which leads to a decreased heart rate and lower core temp both during exercise and at rest
When Should You Incorporate Heat Acclimation?
Direct heat acclimation – daily exposure to the race-day environment – happens in about 10-14 days. But not everyone can arrive at their race location 2 weeks ahead of time.
If you need to acclimate to the heat prior to arriving at the race location, we recommend starting 4-6 weeks before race day – because heat acclimation is taxing on your system and creates fatigue, you don’t want to do this during taper, when you are trying to reduce training stress.
You’ll incorporate heat acclimation protocols into select workouts over 2-3 weeks to become acclimatized. Retaining the physiological adaptations of heat acclimation requires weekly maintenance over the final weeks leading into race day.
Heat Acclimation Protocols
Recent guidance promotes active heat acclimation protocols over passive protocols (e.g., sauna usage). We recommend executing 60-90 minutes of easy/endurance work (not interval/high-intensity work) in a hot environment three to four times per week during your heat acclimation weeks, and one to two times a week when maintaining acclimatization.
The hot environment can be achieved indoors – such as during trainer rides and treadmill runs – by wearing extra layers of clothing, using a space heater, and/or turning off your fan. Outdoors you can train during the hottest time of day and add layers to increase your core temperature. The goal of these tactics is to raise your core temperature during training – if you are not uncomfortable, you are not going to elicit the desired adaptations.
One additional option for heat acclimation is hot yoga – the combination of heat and and an elevated heart rate are ideal for heat acclimation.
Dealing with the Heat on Race Day
Even with solid pre-race heat acclimation training, you may still find yourself wilting in the heat on race day. See our tips on Racing in the Heat for race day heat-management strategies.