"Listen to your body and drink enough"

It's summer – there are beads of sweat on your brow and every movement takes more effort than ever. So is it really a good idea to exercise in the heat? Prof. Dr. Daniel König is a doctor specializing in internal medicine and cardiology with a focus on sport and dietary medicine amongst other things. He heads the Nutrition Unit at the Institute of Sports Science and Physical Education of the University of Freiburg. Emilie Häberle asked him about exercise and diet in hot weather.

Swimming offers a blend of effort and cooling.
Photo: Dasha Petrenko/Fotolia

Mr. König, it's common in the summer here to see cyclists on the Schauinsland mountain in the midday heat – what do you think about this?

As long as their physique can handle it, I don't think there's a problem. What's important is that they have to restore the huge amount that they sweat with drinks. In temperatures of 28 to 30 degrees Celsius it is entirely possible that you lose between one and one and a half liters in sweat per hour.

Sports in the summer: Daniel König explains what you should think about when training in hot weather.
Photo: Thomas Kunz

What is the best thing to drink in the heat and after training?

We have to distinguish between everyday activity and sporting activities here. For extended periods of exercise in endurance training, the drink should contain six to eight per cent carbohydrates. But for a normal person who isn't doing intensive endurance sports I would avoid sweetened drinks such as Coke or Fanta – but also fruit juice spritzers – and instead use unsweetened fruit teas or best of all water. Because sweetened drinks affect our calorie balance detrimentally. They have a high proportion of carbohydrates and therefore also calories. This is particularly important when you think that recent studies have shown that about 60 per cent of Germans suffer from being overweight.

Which food helps you cope with the heat? And which should you avoid?

Really there are no recommendations for this, you should just listen to your body and your appetite. Many find very fatty and heavy food off-putting, because your body – which already has plenty to do with adapting to the heat – doesn't want to spend long digesting as well. If you just want to eat a chilled melon in the evening, there's absolutely nothing wrong with that.

Is it a good idea to exercise in the heat or could it be dangerous?

Physical activity and sport are always a good idea in principle, however if the heat is too intense there is the risk of a heat shock. It's not a good idea to go jogging on asphalt at 34 degrees Celsius in the blazing midday sun – so the recommendation is clearly that you should choose either the morning or the evening. If you want to exercise in hot weather, or even have to, you should however take care of a few things. These include ensuring that the fluid balance is maintained and that you watch out for symptoms of impending heatstroke, such as a headache, rapid pulse, dizziness, and red, often dry skin. It's also important to know that there is no additional training effect if you exercise in intense heat.

Why are sporting activities more demanding in the heat?

During sporting activities the majority of our organism is busy cooling the body and maintaining core body temperature. So the heart has to work harder to do this and the hormonal system is also under stress. The amount of the blood volume used for cooling is no longer available to our musculature to supply energy and oxygen, and this accelerates fatigue.

What should you remember when training in the heat? Which types of sport are better and which maybe not?

One clear recommendation is swimming – but to train of course, not in the play pool. Lane swimming combines pleasure and sport. Other highly-suitable types of sport include those where our bodies are nicely cooled by the breeze, such as cycling.

What sport do you do yourself in the summer?

I'm not by nature someone who likes to exercise in the heat and at high temperatures – I prefer to do things in the evening or early morning. But really, like with food, you just have to listen to your preferences and see what does you good. If it's possible, I take the bike to work because even burning a few calories each time spread over the day counts.