Strategies to Prepare for the Heat
by Doug Stewart
I recently raced the Calamorro Skyrace in southern Spain, in the middle of a national heat wave, and with the race taking place on the hottest day so far. Plus, it started at 3pm, the hottest time of day. Unsurprisingly, I witnessed a number of runners suffering in the heat, and at least one athlete was hospitalised with heat stroke.
Although I had not known just how hot it would be until a day or two prior, when the forecast was updated, I had expected it to be hot compared to my usual training environment. This is why I adopted the following scientifically backed strategies to help mitigate the impact of the heat.
Heat Acclimation
A 2022 study compared the impact of 12 days of a hot bath (hot water immersion to give it the name they used – but it was sitting in a hot bath) after a run, compared to running in the heat, and a control group.
The below graphic provides a summary of the intervention.
Source: McIntyre et al., 2022
The researchers discovered that taking a hot bath after a run resulted in greater adaptations than simply running in the heat. Importantly as well, although they did 12 days, they tested the subjects after 3 and 6 days of the protocol, too. After 6 hot baths, most of the benefits had already been achieved. Additionally, the format of this protocol was 3 days of baths, a rest day, and then the first assessment day. This was followed by 3 more days of hot baths, a rest day and another assessment day. The final block consisted of 3 days of baths, a rest day and the final test. So, hot baths were not taken day after day, but included 2 days of breaks.
A practical takeaway for athletes racing in the heat is to include hot baths in the final week or two before the event. This will add additional ‘stress’ so, if adding them into a heavy training load, you must be mindful and adapt training as required. Furthermore, hydration will be important, as you will be sweating in the bath if the protocol is done properly.
Prior to Calamorro, I took 8 baths over 11 days. I did not do a bath the two days prior as I wanted to ensure I was properly hydrated going into the race and I missed one day due to travel in the build-up. My first two baths lasted 20 minutes, then 25 minutes (post runs), then 40 minutes on a rest day, and the remainder were around 40 minutes in duration after a run.
Pre-Race Cooling
A 2021 study discovered that pre-race head cooling improved 5km run times. The subjects were not highly trained athletes, but the group that had 20 minutes of pre-race head cooling (the rest of the body was at an ambient temperature) ran the 5km faster than when sat in the same ambient temperature for 20 minutes prior to the run without head cooling. Interestingly, both core and head temperatures were lower when the head had been cooled.
Prior to Calamorro, I made my sun hat wet, and then put it in the freezer. For my walk to the start line I had a slowly defrosting cap on my head. It was maybe only cool for 10 minutes, but it certainly felt nice. If I had had access to ice cubes, I would have put these under my hat as well.
In Race Cooling
For this, there were 3 areas of focus for me: cooling vest, head cooling, ice ingestion.
Cooling Vests – a 2023 meta-analysis exploring the use of cooling vests in various sport settings found that they impacted the perception of heat and performance. My approach was that I had always planned to carry 1.5l of fluid at the start, so I froze my 3 soft-flasks (I then started with a 4th unfrozen one when I saw the temperature) and also put my gels in the freezer (my gels did not freeze, others may, depending on water content). I tested this approach twice before the race. I then started the race with 2 frozen bottles against my chest and one in a back pocket, with my gels in the side pockets. They then defrosted in the first hour and hopefully had a positive impact on my temperature.
Head Cooling – a 2022 study explored the impact of head cooling during a 5km time trial. Like the pre-cooling results, when the subjects ran with a cooling hat, they recorded a lower temperature at their head level, as well improved thermal comfort. They also ran faster. For this, although harder to do, I put one of my partially defrosted water bottles under my hat for the second climb (when I was hiking rather than running). This felt like a more noticeable cooling versus where the bottle had been in my vest. At the aid station, I soaked my hat in the water available.
Ice Ingestion – another 2022 study explored a cooling hat and ice ingestion. There were three scenarios:
1. Head cooling during exercise (HC)
2. Ice ingestion prior and then head cooling during (Mix)
3. A control group.
The HC and Mix approaches both saw improvements in cognitive function during the exercise, but the mix group saw a reduction in core temperature not seen in the HC group. This suggests that a pre-cooling strategy coupled with in exercise cooling offers greater opportunities for mitigating the impact of the heat.
Whilst I did not ingest any ice prior to the race, I did use the freshly melted bottles to drink from, which certainly felt cooling, and had my pre-race head cooling approach as mentioned above.
All in all, there is a lot of recent evidence validating a lot of the approaches we would maybe naturally use, and some you may not have thought of. Hopefully, you can trial some of these in training and, if they work for you, adopt them for hot races you may have coming up.
References:
Coelho, L. G., Ferreira‐Júnior, J. B., Williams, T. B., Maia‐Lima, A., Borba, D. A., Silva, C. D., ... & Silami‐Garcia, E. (2021). Head pre‐cooling improves 5‐km time‐trial performance in male amateur runners in the heat. Scandinavian Journal of Medicine & Science in Sports, 31(9), 1753-1763.
Fernández-Lázaro, D., García, J. F., Corchete, L. A., Del Valle Soto, M., Santamaría, G., & Seco-Calvo, J. (2023). Is the Cooling Vest an Ergogenic Tool for Physically Active Individuals? Assessment of Perceptual Response, Thermo-Physiological Behavior, and Sports Performance: A Systematic Review and Meta-Analysis. Bioengineering, 10(2), 132.
Mazalan, N. S., Landers, G. J., Wallman, K. E., & Ecker, U. (2022). A combination of ice ingestion and head cooling enhances cognitive performance during endurance exercise in the heat. Journal of Sports Science & Medicine, 21(1), 23.
McIntyre, R. D., Zurawlew, M. J., Mee, J. A., Walsh, N. P., & Oliver, S. J. (2022). A comparison of medium-term heat acclimation by post-exercise hot water immersion or exercise in the heat: adaptations, overreaching, and thyroid hormones. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 323(5), R601-R615.
Spannagl, B. J., Willems, M. E., & West, A. T. (2022). Effects Of A Head-Cooling Cap On 5-Km Running Performance In The Heat. International journal of exercise science.