The Vierdaagse week has a chance of reaching tropical temperatures. How can participants best deal with this? Exercise physiologist Thijs Eijsvogels has come up with four tips. ‘Check the colour of your urine every now and again.’

It’s not quite clear yet how hot it will be at the start of the Vierdaagse – different models come up with different results. But there’s a good chance that on Tuesday the 42,000 participants will be sweating up a storm.

Hikers had best prepare for those kinds of temperatures, according to physiologist Thijs Eijsvogels of the Radboudumc, who is also a member of the Vierdaagse emergency services. He investigated how both athletes and audience members could best prepare for tropical temperatures at the 2021 Tokyo Olympics.

According to Eijsvogels, the most important thing is to listen to your body: ‘If you’re not feeling well, take a break’. Eijsvogels has come up with four tips specific to the Vierdaagse.

1. Wear breezy clothes

People like to dress lightly when it’s warm. But it’s not just the amount of clothes that’s important. ‘Make sure to wear light, breezy clothes’, Eijsvogels says. ‘Those are the best at releasing heat and moisture. Try to avoid cotton shirts.’

‘It’s a good idea to wear a cap or a hat’

The colour of your clothes is another important factor. ‘Wear mostly light colours and avoid black. That way, the sun won’t have as much effect on your body. It’s also a good idea to wear a cap or a hat, so that your head is shielded from the sun.

2. Adapt your speed

Vierdaagse participants are used to maintaining a certain speed. ‘But that also determines how much heat your body produces: using your muscles releases heat, which raises your body temperature. By walking a bit more slowly, you will produce less heat and your temperature won’t rise as quickly.’

However, according to Eijsvogels, maintaining a slow speed throughout the day can also have adverse effects, since that means more exposure to the heat. ‘Try to keep a quick pace in the morning when it’s still relatively cool outside. Then change your tempo when it gets hotter and take a break every now and then.’

3. Drink plenty of fluids

Dehydration is a real risk in warmer temperatures. ‘When you’re dehydrated, walking will be much more difficult and your body temperature will rise much quicker’, according to Eijsvogels. That is why it’s so important to drink plenty of fluids: this will make you sweat more, which the body uses to dissipate heat. ‘You tend to sweat more in higher temperatures, which means you need more fluids. It’s very important to keep an eye on that.’

‘Be careful with sodas, as those can upset your stomach’

How can you tell you’re drinking enough? ‘You can check this by examining the colour of your urine. If it’s clear, you’re okay. But if it’s darker or yellow, you need to drink more.’

Exactly how much you should drink depends on certain factors, including age, sex and body type, and will also vary throughout the day. What kind of fluids you drink also plays a part. ‘You should drink either water or sports drinks. Be careful with sodas, as those can upset your stomach. It’s also good to maintain drinking habits from your training schedule.’

4. Try and acclimate to the heat

The next few days will also be very warm, which is an excellent opportunity to get your body acclimated to the heat, according to Eijsvogels. ‘The human body was made for warm surroundings; the first humans wandered in the savannah, after all.’

The human body is also very good at adapting to heat. ‘Don’t spend your days inside airconditioned rooms but try training outside in warm weather. That’s how you’ll teach your body how to handle the heat. This will make you sweat more easily and lower your heart rate. If you’re used to the heat, you’re better at handling it.’