The first signs of overheating are harmless symptoms such as dizziness, nausea and fatigue, says Coen Bongers of the Radboud University Medical Center - he conducts research into heat and sports performance. 'The body tries to keep the temperature around 37 degrees. How do you know if you are drinking enough water. If the temperature rises, by effort or by ambient heat, problems can arise. What you mainly see is heat cramps in the muscles, perspiration and headaches. "Certainly in the combination of heat and exertion, the body temperature can rise quickly, says Bongers, because the ability to release heat is limited.
On the internet, many tips circulate to keep the body cool on summer days, ranging from putting sheets in the fridge, spicy food or taking an ice bath. It is indeed possible to keep the body cool in various ways, says Bongers. 'Carrying a cooling vest, drinking ice shavings or taking a cold shower prior to an effort creates a larger buffer to be able to rise in temperature. At rest it also helps to drink enough, to stay out of the sun, to wear light clothes and to stay in a cool environment, so that the body can lose its warmth. '
Once overheated, there are completely different measures to advise. The most frequently heard tip that provides a lot of discussion at the same time is drinking cold water. It would either cool the body down, or it would actually encourage you to work harder to deal with the cold, which would cause the body to warm up. Is not a cup of tea better?
Lose weight by drinking water. Drinking too cold is not sensible, says Bongers. Overheating can best be combated by gradually cooling the body. 'What you really want is to open your blood vessels to release more heat. If you drink too much cold water too quickly, the blood vessels will narrow themselves; that has an opposite effect. "The same applies to a cold shower: better is lukewarm water. And that cup of tea? Canadian researcher Ollie Jay tested the idea in his Thermal Ergonomics Laboratory with cyclists he was using sensors (Acta Physiologica, October 2012). The conclusion: a cup of tea indeed helps to cool down, but only under certain circumstances. "What we discovered is that you start to sweat disproportionately when you drink a hot drink," Jay told Smithsonian.com. "Yes, a hot drink is warmer than your body temperature, but the increase in sweat - if that can at least evaporate - compensates well for the added heat." The core temperature of the body does not increase, incidentally, Jay discovered. And the sweat must therefore be able to evaporate. 'On a very hot and humid day, or if you wear a lot of clothes, and the sweat can not evaporate from the skin, a hot drink is a bad idea.'
The ability to deal with heat better - for healthy people - can be trained, says the Nijmegen Bongers. Athletes are already better on average. 'Athletes are more often exposed to physically stressful conditions, making their bodies sweat faster and release heat more easily,' says Bongers. "Acclimatizing in a warm environment also helps to learn how to give off heat better." So let that heat wave last for a while. Soft drinks, up to 7 cubes of sugar. Healthy drinks instead of water.