How to adjust to the summer heat without major changes to your training.
The sound of cicadas cuts through the air while the sun beams relentlessly through fresh leaves and into the blacktop of familiar roads. Meanwhile, a mapped trail, faded from months of a similar sun’s persistence, prepares for the tenacity of athletes from farther, cooler climates. Summer is here, and so too are the races that accompany these months.
Heat acclimation is your body’s adaptation to this climatic change, and it can be manipulated to improve your performance in unfamiliar conditions. Many athletes choose to incorporate heat acclimation strategies in the weeks prior to an athletic event in a hotter climate, but casual runners can just as easily use it to prepare for the incoming summer months.
Carl James, a researcher at Hong Kong Baptist University, predicted athletes’ need for answers just last month, April 2024, when he published a method for heat acclimation supported by improved outcomes in triathletes. James’ work specializes in the effects of extreme heat on physical performance, and he has been collaborating with athletes in this area for years. James said, “This paper was basically born out of trying to work out for one particular event, how best to prepare the athletes within their set of circumstances.”
Accessibility was James’ primary focus; he said, “That [accessibility] was the performance puzzle we were trying to solve.” Triathletes bare one of the highest training loads with three different events to prepare. Therefore, it is essential that a heat acclimation program does not add any additional stress or time that could otherwise deter their core training.
James said, “As athletes, you’ve got to deliver when it’s really hot.” Therefore, an understanding of the benefits, approaches, exceptions, and safety measures of heat acclimation can help you bring your training to the next level.
Benefits to Heat Acclimation
- Cardiovascular Adaptations
It is no question that running improves cardiovascular heath, but specifically targeting heart health can be overlooked in favor of more strength-focused training. Heat acclimation can cause a lowered exercise heart rate, greater stroke volume, more stable cardiac output and blood pressure response, improved heart muscle contractions, and improved skin blood flow. These factors result in increased strength for both speed and endurance sessions as well as improved thermal regulation.
- Reduced sodium concentration in sweat
Nothing signals a good workout like a sweat-soaked t-shirt. Heat acclimation can lower temperature thresholds for sweating, so you sweat more and cool down quicker. Reduced sodium concentrations also prevent electrolyte loss, so your body can be more efficient in nutrient consumption and energy output.
- Rate of Perceived Effort and Metabolic Adaptations
Though less reported and more individualized, some athletes reported improved thermal perception and lower ratings of perceived exertion (RPE), suggesting that higher intensities feel easier than prior to heat acclimation. Furthermore, in non-elite populations, athletes had lower metabolic rates, improved VO2 max (the maximal amount of oxygen you can uptake), and reduced rates of glycolysis supporting more efficient nutrient consumption.
- Heat shock proteins (HSPs)
Acute and chronic elevated HSPs support heat adaptation and gut epithelial cell structure. These conditions can improve thermal regulation and mitigate gastrointestinal distress in heat – meaning less time in the bathroom and more time on your feet during a hot race.
Heat Acclimation Approaches
- Passive heating protocols
James’ study mainly focused on passive heating because it provides one of the least stressful implementations for high performing triathletes. Namely, a hot water bath or sauna session after a workout provided optimal heat adaptations before a race. James said, “They’re [saunas] really convenient because you can potentially do them at home, they’re not adding extra load on your body, and it’s quite time efficient as well.”
- Training twice on non-consecutive days
Following a high intensity workout with a low intensity session in a hot climate could allow your body to regulate to heat faster from the added stress of the day. However, ensuring ample recovery time is necessary to not deter progress, and many athletes are not willing to incorporate any extra rest days to their program prior to a race.
- Completing regular training whist overdressed
This method loses some effectivity but outweighs the other options in accessibility. Just layer up on warm clothes before taking on your typical workout to improve heat adaptation.
Mixed Method Incorporation
Finding out the right method for you requires a retrospective analysis separate from the activities of those around you. That is why a mixed-method approach can be the most effective general guideline, so you can adapt your program to fit your needs.
James said, “Mixed method basically means you’re using a combination of active and passive. Active being that you’re exercising within that hot environment… and getting the benefit of relating those sensations and feelings to what you might experience in your event. The passive side of things is really beneficial because you’re not putting an extra load on your body; it’s also potentially quite convenient.”
In a previous study, James observed head adaptations in a FIFA world cup referee. He followed up his overdressed runs with a hot bath to prepare for the heat of the event location and was able to successfully fulfill his responsibilities.
James suggests 30-40 hot bath sessions 3-4 times a week for up to two weeks depending on your fitness to gain optimal adaptations. He said, “The beautiful thing about heat adaptation is that it occurs quickly.” In many cases, a special program may not even be necessary. If you’re an avid runner, you will experience a natural adaptation anyway – though not as effectively.
Nutrition can play a factor too. Ingesting sodium for electrolytes, carbohydrates for energy, and L-glutamine rich proteins to elevate heat shock proteins can increase the timeline of your heat adaptation.
Safety Tips
Safety should be the number one priority in any changes to your training plan. Although the mixed-method approach aims to avoid added stress, it is still important to play it safe in the heat. The following tips should serve as guidelines before implementing heat acclimation.
- Monitor hot water bath temperatures to maintain heat under 105° F. It should be comfortable to put your wrist under the water.
- Phone a friend to check on you after new implementations such as overdressing or hot water baths.
- Make these decisions with a coach if it is available to you.
- Consider extenuating circumstances. For instance, women can experience changes in their core temperature and thermal regulation systems at various points in their menstrual cycle. Learn what works best for you.
Don’t let the heat this summer deter you from your next race or long run. It can be daunting to feel temperatures rising, but our bodies are resilient and capable of extraordinary feats. James said, “This mixed approach has a lot of value because it can be flexible to whatever that individual athlete training program is, what they’re needs are, and what works for them.” While an efficient, tried-and-true method is exciting, be reassured in the fact that you will adapt regardless of your preparations.
Take in the warm sun, smell the blooming flowers, and admire the excitement buzzing around everyone you pass. Summer running, for all the disadvantages of its high temperatures, brings out a lively community that ultimately feeds a deeper passion for the sport.
Sources
James, C.A., Willmott, A.G.B., Lee, C.W.D. et al. Mixed-Method Heat Acclimation Induces Heat Adaptations in International Triathletes Without Training Modification. J. of SCI. IN SPORT AND EXERCISE (2024). https://doi.org/10.1007/s42978-024-00278-9
Oliver R. Gibson, Carl A. James, Jessica A. Mee, Ashley G.B. Willmott, Gareth Turner, Mark Hayes & Neil S. Maxwell (2019): Heat alleviation strategies for athletic performance: A review and practitioner guidelines, Temperature, DOI: 10.1080/23328940.2019.1666624