Does fitness crossover from training in heat, humidity, or at altitude?

Each extreme climate stresses your body in different ways, but some of the adaptations you gain can actually carry over.

This concept is important to understand, if for example, you have a high altitude mountain race coming up , but you live at sea level, somewhere humid forcing you to get creative with your training.

To maximise benefits in your situation, the real trick is understanding which types of training overlap, and where those benefits stop so that you can better simulate the environment in which you'll be racing.

Can training in one extreme environment help you perform better in another?

The short answer is YES—thank goodness! Training in heat or at altitude creates cardiovascular and thermoregulatory adaptations that can potentially improve running performance in other challenging environments.

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However, these adaptations are condition-specific. So, while training in one tough climate can help build general fitness and resilience, it won’t fully prepare your body for all the others.

How heat affects your running performance

Running in the heat puts your body into overdrive. Your core temperature rises, blood flow gets redirected from muscles to the skin, and your heart rate spikes.

Everything feels harder—even easy paces.

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Adaptations from heat training:

• Increased plasma volume (improves circulation and cooling)
• More efficient sweat response (you sweat earlier and smarter)
• Lower heart rate at submaximal efforts after acclimation

Heat training crossover potential:

Training in the heat can improve cardiovascular efficiency, which may help at altitude by boosting oxygen delivery.

If you’re prepping for a high-elevation race but don't live in the mountains, heat training is a decent stand-in.

To compliment this, I'd recommend throwing in some training sessions on a treadmill, wearing an elevation training mask to help simulate the thin air.

How humidity impacts your body while running

Humidity makes running feel even harder than heat alone. When the air is saturated, sweat can’t evaporate properly—so your body struggles to cool itself down.