Drinking in heat and sport: amount, salt, timing

What heat does to the body

Sweating is the body’s air conditioning. On hot days two to three litres can easily evaporate, and up to 1.5 litres per hour during sport in the sun. If you do not replace that, you get headaches, dizziness and a fast pulse. From two per cent weight loss, performance measurably drops; from five per cent it becomes dangerous.

The plan

• Before: In the two hours before sport, about 500 ml, in small sips so that you do not start with a full stomach.
• During: Every 15 to 20 minutes, 150 to 250 ml. For exertion of up to an hour, water is enough.
• Over an hour: Now salts are lost with the sweat, above all sodium. A high-sodium mineral water, a pinch of salt per litre or diluted juice with salt replace it.
• Afterwards: Drink 1.5 times the weight loss, spread over the next few hours.

Why water alone is sometimes not enough

If you sweat for hours and drink litres of plain water, you dilute the sodium in your blood. This is rare, but it is a real risk in marathons, long-distance cycling events and hikes in the heat. For long exertion, therefore, always add salt or a drink with electrolytes. Alcohol-free wheat beer and apple spritzer mixed 1:2 are proven classics.

Cold or warm?

Cool drinks at around 10 to 15 °C are best tolerated in the heat and cool you from the inside. Ice-cold drinks slow absorption and can cause stomach cramps. Hot tea in the heat, as is common in many warm countries, stimulates sweating and so also cools, but it is a matter of taste.

For children and older people

Children feel thirst later and forget to drink while playing. Older people have a weaker sense of thirst and often take medication that dehydrates. For both, a fixed rule helps: a glass every 30 minutes, regardless of thirst. More in the article Water for children and seniors.