While the focus of optimal indoor training is to control two critical variables — intensity and duration —heat is another powerful tool to develop fitness and get faster.

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Before you throw away your fan…

Foremost, it’s important to acknowledge our stance on cooling. In almost every situation our suggestion for managing heat indoors is to do all you can to eliminate it. Core body temperature has a profound impact on the body’s capacity for work. Since the goal of most structured training is to increase the body’s work capacity, keeping your body cool with a good fan or cool environment will allow you to more effectively exploit your existing capacity and increase it to new levels.

That said, there are proven upsides to going the opposite direction and embracing heat, as long as it is applied correctly.

How to Implement Heat Training

Heat training is about as straightforward as it sounds, but there are goals and methods to help get the most from this approach.

Firstly, the goal of heat training is to elevate core body temperature from a typical ∼37°C/98.6°F to some point within the narrow functional range of ~37.3-39°C/99-102°F. This is easily done by training in ambient conditions that also fall within this range. Whether this is done in an enclosed space like a steamy bathroom (we talk this exact experience in episode 103), sauna, or any warm enclosure, one thing to keep in mind is that the performance benefits of heat training are more reliably and quickly achieved in dry environments rather than humid ones.¹

While training in the heat, power output should be expected to drop as much as 5-7% for a given exertion level, and so too should your ability to sustain high levels of power output for extended periods of time. In other words, heat training is most easily paired with low-intensity workouts, and it still delivers the desired adaptations.²

Studies have shown heat training to be effective with as little frequency as a 100-minute session every three days, but any less frequency will not allow your body to retain the desired benefits.⁴

While the benefits are less clearly documented, exposure to heat directly after a workout in a sauna is also considered to be beneficial. (In episode 45 we cover the science behind sauna usage as a training tool.)

The Performance Benefits of Heat Training

As you train in the heat more regularly, an obvious benefit is a greater tolerance to working in hot conditions. This is largely due to an increase in blood plasma volume which improves your ability to shed heat through sweating. When properly implemented, your body will sweat at lower core temperatures and your sweat will contain less electrolytes, increasing resistance to significant losses of important micronutrients and making evaporative cooling more effective.

This increase in thermoregulatory efficiency and blood plasma volume means you will have more blood available to tend to the needs of your working muscles. This has shown to provide an increase of 3-8% in submaximal performance and performance at VO2max in hot and cool conditions, with most experiencing an increase closer to 7%.^9 1

Summary

Whether you plan on racing in the heat or are just looking for a marginal gain from your lower intensity training, heat training is effective. Just be aware that it is also extremely uncomfortable, can potentially compromise the quality of your  workout, and if not carefully executed, can be unsafe. It is extremely important to err on the side of caution when training in severe conditions. Listening to your body and medical advisors is absolutely necessary.

To hear us dive deeper into heat training and what we’ve learned implementing it into our own training listen to Episode 103 of the Ask a Cycling Coach Podcast.

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References

1. Lorenzo, S., Halliwill, J. R., Sawka, M. N., & Minson, C. T. (2010, October). Heat acclimation improves exercise performance. https://www.ncbi.nlm.nih.gov/pubmed/20724560
2. Garrett, A. T., Creasy, R., Rehrer, N. J., Patterson, M. J., & Cotter, J. D. (2012, May). Effectiveness of short-term heat acclimation for highly trained athletes. https://www.ncbi.nlm.nih.gov/pubmed/21915701
3. Zurawlew, M. J., Walsh, N. P., Fortes, M. B., & Potter, C. (2016, July). Post-exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat. https://www.ncbi.nlm.nih.gov/pubmed/26661992
4. Hettinga, F. J., Koning, J. J., Vrijer, A. D., Wüst, R. C., Daanen, H. A., & Foster, C. (2007, November). The effect of ambient temperature on gross-efficiency in cycling. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2039810/
5. Kukkonen-Harjula, K., Oja, P., Laustiola, K., Vuori, I., Jolkkonen, J., Siitonen, S., & Vapaatalo, H. (n.d.). Haemodynamic and hormonal responses to heat exposure in a Finnish sauna bath. https://www.ncbi.nlm.nih.gov/pubmed/2759081
6. Leppäluoto, J., Huttunen, P., Hirvonen, J., Väänänen, A., Tuominen, M., & Vuori, J. (1986, November). Endocrine effects of repeated sauna bathing. https://www.ncbi.nlm.nih.gov/pubmed/3788622
7. Scoon, G. S., Hopkins, W. G., Mayhew, S., & Cotter, J. D. (2007, August). Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. https://www.ncbi.nlm.nih.gov/pubmed/16877041
8. Hannuksela, M. L., & Ellahham, S. (2001, February 01). Benefits and risks of sauna bathing. https://www.ncbi.nlm.nih.gov/pubmed/11165553
9. Hagberg, J. M., Goldberg, A. P., Lakatta, L., O’Connor, F. C., Becker, L. C., Lakatta, E. G., & Fleg, J. L. (1998, August). Expanded blood volumes contribute to the increased cardiovascular performance of endurance-trained older men. https://www.ncbi.nlm.nih.gov/pubmed/9688724

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