Safely through the summer: how to avoid heat stress during sport

An article about body intelligence, timing, fluidity - and why you should learn to listen to your body's quieter signals.

There is that one moment in summer when everything seems to slow down. The light lies heavy over the landscape, the air shimmers, even the wind seems sleepier than usual. If you want to be active in this atmosphere, you have to know what you're doing. Because heat is not an enemy, but it is a factor - one that should be taken seriously.

Heat stress refers to the strain placed on the body by high outside temperatures, especially in combination with physical exertion. When you exercise, your body produces heat. Normally, this is compensated for by sweating and increased blood flow to the skin. However, if the outside temperature rises sharply - especially above 30 °C - and there is also high humidity, this cooling system reaches its limits. The result: dehydration, circulatory problems, lack of concentration - in the worst case, heatstroke.

Something that is often underestimated: The physiological response to heat doesn't just start with sweat. Even a moderate rise in temperature changes your blood volume, your cardiovascular system works harder and blood flow to your muscles can be restricted. All of this costs energy - energy that you then lack when exercising. Therefore, if you train outside in summer, you not only need willpower, but also knowledge.

The best time of day for sport in summer is early in the morning - between 6 and 9 am. The air is still cool, UV exposure is low and ozone levels are manageable. If you can't be active in the morning, it's better to switch to the late evening hours. Between 11am and 5pm, intensive outdoor exercise is taboo - unless you're looking to take a risk.

Pro tip: On hot days, favour indoor training or forest running - the difference in perceived temperature can be enormous.

Depending on the type of sport, fluid loss through sweating can be between 0.5 and 2 litres per hour. A fluid deficiency of just 2% of body weight can significantly reduce performance. But: If you only drink when you are thirsty, you are drinking too late.

UV rays are not only enemies of the skin, they also weaken the immune system - and can lead to sunstroke or heat exhaustion if overused. Therefore:

Most symptoms of overheating appear gradually. Typical early warning signs:

Summer means energy, movement, freedom - but also responsibility. Those who train outdoors are not playing against nature, but with it. That means tactics instead of defiance. Drinking instead of bravery. And above all: honesty with yourself. You don't always have to go faster, further, harder. Sometimes the smartest thing you can do is to stop earlier - or start later.

Because the summer is yours. But only if you enjoy it wisely.