• Running in hot weather

Running in hot weather

The risk of heat problems increases when the temperature and humidity rises. A sudden increase of the temperature raises the risk of heat problems even more. This is because we are less used to practice sport with a high temperature. If you practice sport in warm conditions you will get used to that, this is called acclimatization. During acclimatization changes occur in the body which makes it able to deal with the circumstances in a better way. Heat problems during running can happen to every runner. Even at a temperature of 18 degrees a runner can get overheated because of the effort that is delivered. Heat-related conditions include

Heat cramps

Heat cramps are relatively common. They involve painful contractions of the muscles (usually the calf muscles). They are caused by a combination of loss of body fluid and strenuous and/or prolonged strain on your muscles. The best way to treat heat cramps is to gently stretch and massage the cramped muscle and drink (a sports drink) to replace lost body fluids.

Heat exhaustion

Heat-exhaustion can occur when the body generates more warmth than it can lose during exercise. The risk for this is at its highest under warm, damp circumstances, when there is not enough drinking for and/or during exercise, when the clothing is too warm and when the runner is not used to these circumstances. Heat exhaustion typically induces flu-like symptoms. Exercise can cause body temperature to rise as high as 40°C. Signs of heat exhaustion can include headache, feeling nauseous and inability to maintain the same pace. It is important to take heat exhaustion seriously. If left untreated, it can quickly turn into heat stroke (see below). The best way to treat heat exhaustion is to lie the person down in a cool spot and lower their temperature by applying ice packs to their neck, armpits and groin, splashing the body with cold water or applying wet towels.

Heat stroke

A heatstroke is a very severe illness, which can lead to mortality when interfering too late. Early recognition and treatment is therefore of great importance. When somebody develops heat stroke, their internal body temperature can rise above 40°C, impairing nervous system function. Symptoms include headache, confusion, loss of coordination, convulsions and loss of consciousness. Body temperature needs to be lowered quickly. This can be done by applying ice packs, splashing the body with cold water or immersing the person in cold water. It is important to be aware that heat stroke can also occur on days when the temperature is 18°C. It doesn’t have to be a very hot day!

Tips to reduce the risks of overheating

1. Make sure sweat can evaporate

Wear light, breathable clothing made from loosely woven fabric to enable sweat to evaporate. Dark and heavy clothing increases the risk of overheating. A headband will help keep sweat out of your eyes.

2. Protect yourself from the sun

UV rays can damage your eyes and cause skin cancer. Wear a cap to keep your head cool and protect your face and neck from sunburn. Sunglasses or protective contact lenses are not a luxury in bright sunshine. They help to protect your eyes in the long run, so it’s a win-win situation. So don’t go out without protection the skin with a sunscreen with a good Sun Protection Factor (SPF). We recommend to use at least factor 10 or 12 in the Netherlands.

3. Check the Wet-Bulb Globe Temperature (WBGT)

This might not cause a lightbulb moment straight away. But the WBGT is a reliable indicator of the heat stress the body feels in direct sunlight, because it also takes into account humidity, wind speed and solar radiation. Many sports federations use the WBGT as a guideline to determine whether an event should go ahead.

4. Drink enough but not too much!

On hot days, it is very important to keep topping up your fluid levels. But just drinking water is not enough, because when you sweat you also lose salt. This can lower your blood salt levels (especially your blood sodium level), which can cause problems. So alternate water with a sports drink, because sports drinks contain nutrients that help maintain normal blood sodium levels.

To work out how much you need to drink, it is helpful to know roughly how much you sweat while running. This can differ considerably from person to person! So how do you work out how much you sweat? Weigh yourself before and after training. Ideally, you want to manage your fluid intake so that you don’t lose more than 2% of your body weight, and also don’t weigh more after the event.

This will give you a rough idea of how much you need to drink during the TCS Amsterdam Marathon. Drink two large glasses of water (500ml) with your pre-race meal approximately 2 hours before the race. Your body will then have time to absorb what it needs and excrete any excess. And if it is really hot, be sure to eat something salty. Overheating is more problematic than dehydration, but if you are dehydrated, your body will overheat faster. So splash water on your body and pour a sports drink into your mouth!

Below are some additional tips for participants regarding fluid intake:

  • Always drink large sips at a time, frequent small sips do not stimulate the stomach, so that the stomach emptying is slower;
  • Preferably bring your own water;
  • Don’t drink alcohol before the run;
  • If necessary, use the sponges offered at the water stations to cool yourself down;
  • In general: your urine production should be sufficient (at least 1.5 liters per day). By looking at the color of your urine, you can verify whether you have been drinking enough. Before the event your urine should preferably be light yellow. When the urine is dark yellow, you haven’t been drinking enough.

5. Don’t bother with salt tablets

In the past, runners were advised to consume salt tablets on hot race days, but this is no longer recommended. While it is true that salt is lost through sweat, consuming salt tablets is a bit like drinking salt water: it simply increases your thirst. So drink plenty of fluids to stay hydrated and eat salty foods to replace lost salt.

6. Adjust your pace

You may have been training to set a new personal best, but if the weather is hot, you would be well advised to adjust your pace. Control your speed from the start and keep an eye on your pace: the adrenaline you feel at the start may cause you to set off too fast. Run at your own pace and try to avoid radical pace changes.

7. Use the Red Cross stations

There are Red Cross aid stations at regular 500m intervals along the TCS Amsterdam Marathon route. If you don’t feel well or are having difficulty, Red Cross staff will be happy to help. 

If you are experiencing any of the heat stroke symptoms described above, stop immediately and seek assistance at one of the Red Cross stations. Some runners may not recognise the symptoms in themselves, so also keep an eye on your fellow runners. If they are drifting or unsteady on their feet, take them aside, get them to lie down in the shade and call for help.

8. Clothing 

To be able to lose superfluous body warmth, the right choice of clothing is essential. Make sure you don’t cut down on clothing and use high-quality. The next tips will be useful for that:

  • Don’t dress too warm and choose clothing that limits the sweat evaporation, so use breathable clothing
  • Don’t expose yourself to warmth on the day of the event, so no warm clothing
  • White clothing has the best reflection of warmth from its environment, the opposite effect black clothing has. White clothing therefore is preferable.
  • Protect your head and neck when exposing to direct sunlight is inevitable (breathable cap)
  • Use sunglasses to protect your eyes against bright sunlight

Make sure to remove your sweating clothes as soon as possible after the event and put on some clean and dry clothes. This is important because the sweat in your sporting clothes cools down very quickly which will cool down your muscles as well.

9. If it has happened before, be extra careful!

People who have overheated in the past are more susceptible. If this applies to you, be extra careful when running on hot days. Children, older people and those who have a health condition or are unfit are generally more at risk of overheating. It is best for them to avoid intense and prolonged exertion in hot weather.

10. Acclimatization

Try to train on a warm day in your preparation for the TCS Amsterdam Marathon. By doing this you can learn how your body reacts to warmth an the signals you will get. Also your body can get used to running in warm circumstances (acclimatization) so it will be better prepared for possible warmth during the TCS Amsterdam Marathon.

Tips from The Red Cross

The Red Cross held a survey amongst Dutch runners and came to the conclusion that when it comes to preventing a possible overheating, signs of the body shouldn’t be ignored. On their website you can read several advises and results of this research.