The Smart Way to Use Heat Without Ruining Training

Endurance athletes have long used altitude training to upgrade their physiology and boost performance.

 

The classic concept of "Live High, Train Low" was developed to capture the benefits of high-altitude living—primarily increased red blood cell production—while preserving workout quality by doing key sessions at lower elevations.

 

A well-run 3-week camp using this method can bump VO2max by about 4%, thanks to improved oxygen-carrying capacity.

 

The downsides are the travel logistics, added stress, and higher costs—unless you happen to live in an endurance sweet spot especially equipped for this lifestyle, like Flagstaff, Mammoth Lakes, or Salt Lake City.

 

To sidestep the hassle, heat training emerged as a more accessible alternative, sometimes referred to as the poor man's altitude training.

 

A review comparing heat and altitude adaptations credits Storme Heathcote and colleagues with coining the phrase "live cool, train cool, acclimate hot" as a strategy that preserves training intensity in cooler conditions while incorporating post-exercise heat exposure (via sauna, hot-water immersion, or heat chamber) to drive additional adaptations.

 

I've heard of athletes who will suffer in their hot car post-run to get their heat training, but the Heathcote review delivers the scientific recipe:

• Heat dose – ≥ 30 min once-daily, on consecutive days (6–7 exposures can move the needle; 8–14 days is "sweet spot").
• Modalities & temps – sauna ≥ 80 °C (176 °F); heat chamber 45–50 (113°-122°F; hot-water immersion ~40 °C (104°F) to the neck.
• Core-temp target – 38.5 °C; going hotter adds strain, not extra benefit.
• Combine with training – finish your temperate workout, rehydrate a bit, then jump in the heat. The exercise-then-heat combo sparks larger plasma volume gains, heat-shock protein expression, and, in some studies, ~5% faster 5-km performance in the heat.

What kind of improvements can you expect from all this extra sweating? 

 

While both heat and altitude training aim to boost endurance, they work through different physiological levers. 

 

Altitude increases hemoglobin, the oxygen-carrying protein inside red blood cells, resulting in enhanced oxygen delivery and improvements in VO2max. But these gains require sustained exposure above ~2,000 meters (~6,500 feet), and even then, results can vary from person to person.

 

Heat training, by contrast, works faster. It primarily expands plasma volume, the mostly water portion of your blood, which improves thermoregulation, increases stroke volume, and lowers heart rate during submax efforts.  

 

When it comes to actually boosting VO2max in trained athletes, plasma volume alone appears to be insufficient, but there is some emerging evidence that specifically adding heat exposure with training may increase hemoglobin mass. 

 

Still, those results aren't as consistent or predictable as with altitude, and it appears the biggest gain with heat training is (not surprisingly) improved heat tolerance.

 

Recently, I picked up an infrared sauna at an estate sale, hoping it might give me an edge and help push me beyond my "slightly above-average" runner status.

 

My take is that the heavy sweat is oddly enjoyable. Although I've learned that according to sauna purists, infrared is a joke (they call it a glorified heat lamp).

 

I'm holding onto hope that it will help me with sea level training for a mountain race at the end of the month, but it's more likely to help with training in the higher summer temps.

 

The primary takeaways I'll provide if you're curious about spending more time hanging out in the heat.

• Match the stress to the goal. If you're chasing sea-level PRs in cool weather, altitude still provides a more reliable aerobic boost. However, if you're racing in a hot environment, a 1- to 2-week heat block (active, passive, or hybrid) is low-hanging fruit.
• Stack for Maximum Effect. Passive heat allows you to maintain high-quality training sessions while layering adaptation on top—perfect during taper or high-intensity phases.
• Monitor Hydration. Simple weight checks are essential to ensuring you're rehydrating appropriately. It's also recommended to avoid alcohol if you're seeking these heat adaptations.
• Maintain Your Gains. Heat adaptations typically decay within ~1 week; a 2-session "top-up" can help preserve the gains. Hemoglobin decays more slowly (~1% per week), so periodic altitude blocks or even heat blocks longer than 3 weeks could help maintain improvements.