Why exercising in the heat is especially demanding
Physical activity generates heat – and the more intense the training, the more heat the body needs to release. In cool conditions, this happens mainly via the skin's surface and through sweating. However, once outdoor temperatures climb to 28 °C or above, releasing heat becomes considerably more difficult. The circulatory system has to work harder, as it must supply the muscles with oxygen while at the same time directing more blood to the skin's vessels to dissipate heat.
There is also the matter of fluid loss: during intense exercise in the heat, athletes can lose one to two litres of sweat per hour – and along with the sweat, important electrolytes such as sodium, potassium and magnesium. Without proper preparation, this can lead to reduced performance, circulatory problems or, in the worst case, heatstroke.
Exercising in the heat: who needs to take extra care
In principle, anyone can suffer in high temperatures. Particular caution is advised for:
- older people, whose sense of thirst is often reduced
- people with cardiovascular disease or high blood pressure
- people with diabetes mellitus or thyroid conditions
- people who regularly take medication such as diuretics, beta-blockers or certain psychotropic drugs
- untrained individuals or those returning to exercise after illness
- children, as they regulate body temperature less efficiently
In these cases, it is advisable to consult a doctor before exercising in very hot conditions.
Choosing the right time of day and intensity
The simplest yet most effective measure is planning your training time. Whenever possible, exercise in the early morning hours or late evening, when the sun is less intense. The midday heat between 11 a.m. and 4 p.m. should be avoided for intense activity.
Practical training tips
- Reduce intensity by around 10 to 20 per cent on hot days.
- Choose shaded routes, such as through woodland or along waterways.
- Wear light-coloured, breathable clothing and a head covering.
- Use sunscreen with a high sun protection factor.
- Cool down before training, for example with a cold shower or a damp cloth around the neck.
- Listen consistently to your body – on some days, a rest is the better choice.
Drinking during exercise: how much and what?
Drinking during sport is crucial in hot weather. Those who only drink when they feel thirsty are usually already mildly dehydrated. Deliberate fluid intake before, during and after training helps to keep the circulation stable.
Before training
About two hours before exercise, it is recommended to drink 400 to 600 millilitres of water or a light fruit juice spritzer. This gives the body time to absorb the fluid without training being affected by a feeling of fullness.
During training
For activities lasting under an hour, water is usually sufficient. If the activity lasts longer or is particularly intense, drinks containing electrolytes and a small amount of carbohydrate are useful. A proven combination is a mix of water and apple juice in a ratio of 2:1 or 3:1 with a pinch of salt. Take small sips every 15 to 20 minutes, totalling around 150 to 250 millilitres.
After training
Ideally, weigh yourself before and after training. For every kilogram of body weight lost, you should replenish approximately 1 to 1.5 litres of fluid to make up the deficit. Here, too, electrolyte-containing drinks or a balanced meal are helpful.
Heatstroke during exercise: take warning signs seriously
Exercise-induced heatstroke is a medical emergency. It occurs when the body's temperature regulation fails and core temperature rises above 40 °C. It is often preceded by heat exhaustion or heat collapse, which should be recognised in time.
Typical warning signs
- severe dizziness, drowsiness or confusion
- headache, nausea, vomiting
- hot, reddened and sometimes dry skin (sweating may stop)
- a very rapid, shallow pulse
- muscle cramps, weakness in the legs
- visual disturbances or ringing in the ears
- in severe cases, impaired consciousness or unconsciousness
What to do in an emergency
- Stop the activity immediately and move to a shaded, cool place.
- Elevate the legs and loosen tight clothing.
- Cool the body with damp cloths, especially around the neck, armpits and groin.
- Sip fluids in small amounts – provided the person is fully conscious.
- If there is impaired consciousness, persistent vomiting or no improvement, call the emergency number 144 without delay.
Electrolytes: more than just a trend
When we sweat, the body loses not only water but also important minerals. A deficiency in sodium can lead to muscle cramps, circulatory problems and – in rare, severe cases – a dangerous dilution of the blood, if only plain water is taken in. A balanced diet with fruit, vegetables, wholegrain products and dairy usually covers daily requirements. On particularly hot days or during prolonged exertion, isotonic sports drinks or a homemade electrolyte mixture can be beneficial.
Acclimatisation: letting the body adjust to heat gradually
The human body can adapt to higher temperatures – but it needs time to do so. Heat acclimatisation usually takes seven to 14 days. Begin with shorter, less intense sessions and increase duration and intensity step by step. Over time, sweating begins earlier, sweat volume increases, and the salt loss per litre of sweat decreases – meaning the body learns to handle heat more efficiently.
Conclusion: getting through summer with a sensible approach
Exercising in the heat is generally possible, but it requires more attention than training in moderate temperatures. By paying attention to the time of day, an adjusted intensity, adequate fluid intake and the warning signs of your body, you can stay active and healthy throughout the summer. When in doubt, it is better to postpone a session than to put your health at risk.
This article does not replace medical advice.