Heat Training: Is It Really Altitude Training for the Poor?
Reading time: 4 min

Heat Training: Is It Really Altitude Training for the Poor?

Reading time: 4 min
Learn more about one of the most popular training methods in the world of endurance.
Heat Training: Is It Really Altitude Training for the Poor?

Heat training is becoming increasingly popular. You might have heard about it, usually described as altitude training for the poor. However, it’s much more than that, as the effects differ between both methods. 

In this blog, we will take a closer look at heat training, its effects, and the methods available. You may realize that it is a good option for you, too. 

Effects of heat training 

Athletes must have a good reason for choosing to train in uncomfortable conditions. And they do.

The idea behind heat training is a physiological adaptation to heat, which leads to improving endurance performance in hot conditions. At the same time, some studies suggest that the performance of heat-acclimated athletes is also improved in normal conditions.

Lowering body temperature

The main effect we want to achieve is lower body temperature at the same intensity. Normally, our resting body temperature is around 37°C, and our functional range is between 35 and 41°C. That’s a fairly small range, so any improvements in efficiency can have a major impact on performance. 

The range narrows ever so slightly when we take into account study results, which showed that raising body temperature over 39,5°C already negatively impacts performance

With efficient heat training, we can lower body temperature at the same training intensity by 5%. This might not sound like much, but in a world where every second counts, 5% represents a huge advantage.

Humans function efficiently within just 6°C range of body temperature.

Enhanced sweat rate

Another benefit of heat training is the changed amount and composition of sweat. When you get heat acclimated, your sweat rate increases, and you start losing less electrolytes

For example, a heat-acclimatized athlete loses only one-sixth of the sodium per liter of sweat compared to an unacclimatized person. As a result, you get a more diluted sweat. 

The sweat onset temperature is also lowered. This means you start sweating earlier and more, improving evaporative cooling and reducing skin temperature and skin blood flow requirements. 


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Increased body fluids

Heat training also influences blood volume and fluid balance. Studies have shown that it increases total body water by 2-3 L, which is about 5-7% of body weight.

The plasma volume also increases. These changes occur fairly quickly. We usually see them after 3 to 4 consecutive days of repeated heat training. 

It can be argued that extra weight has a negative effect on endurance athletes, especially in sports where the power-to-weight ratio is crucial. We agree to some degree, but the fact is that the advantages of heat training outweigh the extra weight

The more efficient performance makes up for the extra weight.

Changes in blood volume and fluid balance positively affect cardiovascular stability. The heart rate is much higher than normal on the first day of heat training, and stroke volume is lower. Thereafter, the heart rate begins to decrease when exercising at a given work rate due to improved skin cooling, plasma volume expansion, and reduced skin and core temperature

Here is a summarization of the physiological adaptations of heat training:

  • Lower body and skin temperature
  • Earlier and increased sweat rate
  • Reduced electrolyte loss
  • Reduction of heart rate 
  • Expansion of plasma volume
  • Expansion of body water
  • Reduction of lactate accumulation during submaximal exercise 

Heat Training Methods and It’s Implementation 

Now that you know how heat training affects your body and performance, let’s talk about how you can implement it in your training routine. 

Firstly, we need to consider the time needed to experience the positive effects of heat training and how long these adaptations last. About two weeks of daily heat training are needed to get the full effects. 

Figure 1 shows the time course of different physiological adaptations to heat training. After the successful completion of a heat training block, the positive adaptations last for two to four weeks

Heat Training influence on performanceFigure 1: Time course of heat acclimation adaptations with repeated training in the heat. (Source)

There are two different methods of how heat training can be performed. 

Active heat training

The most common method is active heat training. It can be performed in a hot environment (usually 35-38°C) or by wearing a heat suit

Among the popular methods is also a training in a heat chamber, where every parameter can be adjusted. It's also the method Dr. Tim Podlogar uses the most, and he talked about it in the Nduranz podcast, which you can listen to in a video below.

 Active heat training lasts approximately 45-60 minutes and is performed at a low intensity, around 70% of the maximum heart rate. Studies have shown that a body temperature of 38.5°C is optimal for maximal physiological adaptations. 

Temperature sensors can be used to control the body temperature during active heat training, though this is an expensive and unpleasant experience. You can eat a pill that transmits information through Bluetooth, but the pill is quite expensive. A more commonly used method is a rectal thermometer, which is cheaper but much more unpleasant.

Active heat training is the more popular method of the two.

Passive heat training

When you conduct passive heat training, you first do the training session under normal conditions. It’s after that when the passive heat training starts. 

The most common methods of passive heat training are sauna sessions or hot baths.

Spending about 30 minutes in there is recommended to achieve optimal effects.

Passive heat training is done after your regular workout. 


Heat training is an increasingly popular method of performance improvement. It helps you lower core body temperature during training, which leads to more efficient performance. 

When you are heat-acclimated, you sweat more, but the sweat is more diluted as less electrolytes are lost. This further helps with cooling down through evaporative cooling.

The one downside of heat training is the increased water volume in the body, as an acclimated athlete retains about 2-3 liters more water than an unacclimated athlete. However, the performance benefits of heat training outweigh the extra weight.

Heat training is performed in two ways: active and passive. The more commonly used is active, but it can be harder to achieve as you need a hot climate or a heat chamber. As many athletes don’t have that available, a passive method is used in a sauna or a hot tube. 

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