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How does your body react to a summer workout?

heat workout

As an athlete, summer can potentially be a difficult season for training, but it certainly isn’t impossible. As training specialist Christian Soetebier explains, our bodies have some smart mechanisms to deal with heat - up to a point.

How does exercise affect body temperature?

To keep our biochemistry stable, our body temperature is stabilized between 36.1°C and 37.2°C (97F and 99F). This is monitored via receptors and regulated by the hypothalamus within our brain.

When our muscles contract during exercise, the majority of energy we need for this is dissipated as heat. So, depending on workload, straining ourselves may elevate our body temperature as a metabolic reaction.

For example, when training HIIT at 80-90% of VO2max, our body temperature could rise by 1°C every 5 to 8 minutes. However, our body has a smart mechanism that prevents you from overheating: sweat!

Do(n’t) sweat it

When the hypothalamus detects a potential rise in body temperature, the blood flow to our skin and muscles is increased and water is moved to our sweat glands. Shortly after, sweat starts covering our skin. This water then starts to evaporate, cooling our skin.

This metabolic reaction is fine-tuned as you train more and more, especially at higher temperature and humidity levels. This leads to increased sweat production (in comparison to a non-athlete) which facilitates higher performance levels, even during strenuous HIIT workouts in hot conditions. But be careful! As you sweat more and more, you also lose water and risk dehydration.


The statistic commonly cited is that our bodies are made of 70% water. In truth, however, this percentage varies heavily depending on body composition and will most likely fall between 50% and 80%.

Despite what you might think, dehydration is actually a very difficult state to reach for an athlete; it’s more likely that you’ll just get thirsty and that concentrating on this signal will hinder performance. Rather than worrying about dehydration, just drink when you need to. In reality, a low level of dehydration could even be beneficial to performance as it means less weight to carry, but this is something to monitor carefully.

Mental effects of heat and fatigue

However, sweat and dehydration are only one side of the coin: there are psychological consequences of training in the heat as well. Training at higher intensities (i.e. a HIIT session) means that you’ll experience at least some dehydration and hyperthermia on top of the fatigue you’d expect. This will challenge your willpower even more than usual and means that you should plan to train with less intensity than you would at milder temperatures.

Let’s recap:

Training outside in the summer can be a little bit tougher on the body than staying inside an air-conditioned gym. High intensity training under the sun will really push your body physiologically as well as psychologically, but with the right precautions, there’s no reason to avoid the challenge.