Running in warm weather

The risk of heat problems increases as the temperature and humidity rise. A sudden rise in temperature increases the risk of heat problems even more. This is because we are then less accustomed to exercising in high temperatures. When exercising in hot conditions more often, you get used to this, which is called acclimatisation. With acclimatisation, changes occur in the body so that it can cope better with the conditions.

Heat problems during running can happen to any runner. Even at a temperature of 18 degrees, a runner can become overheated due to the effort being exerted. Especially in events that are run at a relatively high intensity (1 to 1.5 hours of effort), the risk of problems in the heat is increased. Watch the information video below and read on to learn more about the conditions that can occur and tips to reduce the risks of overheating.
Heat cramp
A common heat disorder is cramping. These are painful contractions of the muscles, usually the calf muscle. It results from a combination of fluid loss and a large and/or prolonged strain on your muscles. Treatment consists of gently stretching the cramped muscle as well as replenishing fluid loss by drinking (sports drink).

Heat exhaustion
Heat exhaustion can occur when the body generates more heat through exercise than it releases. The risk of this is greatest in hot, humid conditions, if too little has been drunk before and/or during exercise, if too warm clothing is worn and if the runner is not used to the conditions. Heat exhaustion presents a flu-like picture. The body temperature will often have risen to close to 40 degrees due to exertion. The runner often has a headache, is nauseous and can no longer maintain the run pace. Timely intervention is important because heat exhaustion can turn into heat stroke (see below). Treatment for heat exhaustion consists of laying the person down in a cool place and cooling the body by placing ice packs in the neck, armpit, neck and groin or by cooling the person with running cold water or cold wet towels.

Heat stroke
Heat stroke is a very serious condition, which can lead to death if left untreated or too late. So early recognition and treatment is very important. In heat stroke, the body temperature has risen above 40 degrees and the nervous system no longer functions normally. Symptoms that occur are: headache, confusion, loss of coordination, convulsions and loss of consciousness. Treatment of heatstroke involves rapid and intensive cooling of the body using ice packs, cold running water or a cold water bath. It is important to realise that heatstroke can occur even on days when the temperature is 18 degrees; so it does not even have to be extremely hot!

Tips to reduce risks of overheating

1. Sweat must evaporate
Wear light, breathable clothes made of loose woven material so that sweat can evaporate easily. Black and dark clothes actually increase the risk of overheating. A headband will help keep sweat out of your eyes.

2. Protect against the sun
UV rays can damage the eyes and cause skin cancer. A cap will keep your head cool and protect your face and neck from sunburn. Sunglasses or dark contact lenses are no luxury when the sun is bright. And in the long run, this is also better for your eyes: a win-win situation. Also, do not go out without protecting your skin with sunscreen with a good sun protection factor (SPF). We recommend using at least factor 10 or 12 in the Netherlands.

3. Air temperature and WBGT
This may not be the first thing that comes to mind. Air temperature gives an indication of the 'heat stress' the body is exposed to. WBGT (Wet Bulb Globe Temperature) is an accurate method to measure it, as it also takes into account humidity, wind and solar radiation. For sports federations, the WBGT is a good guideline to determine whether events can go ahead or whether additional measures need to be taken.

4. Drink enough, but in moderation!
Moisture and water are the main concerns in high temperatures. But just drinking water is not enough, as sweating also causes you to lose salt. This can cause a shortage of salt (especially the component sodium) in the blood, which can lead to problems. Therefore, alternate water with sports drinks: as these contain salt.

The most useful thing is to know approximately how much you sweat while running; because this can vary a lot from person to person! But how do you find out how much you actually sweat? Then step on the scales every now and then before and after a workout. Try to drink so much that you haven't lost more than 2% of your body weight afterwards, but also not so much that you weigh more afterwards.

Now you also know approximately what you will need in terms of water during the TCS Amsterdam Marathon. Have two large glasses of water (500 ml) with your last meal - about 2 hours before the event - and drink enough (about 2 litres per day) in the days leading up to the event. Now your body has time to absorb it, but you can also get rid of the excess water. Have some extra salty foods if it's really hot. People are more likely to get into trouble because of overheating than dehydration. But dehydration does make you overheat faster. So throw water on your body and sports drink in your mouth!

Here are some additional tips for participants regarding fluid intake:

  • Always drink big sips at a time, frequent small sips do not excite the stomach as well, making gastric emptying slower;
  • Preferably bring your own water;
  • Do not drink alcohol before the run;
  • If necessary, use the sponges offered at the water stations to cool yourself down;
  • General: your urine output should be sufficient (at least 1.5 litres per day). By looking at the colour of your urine, you can check whether you have drunk enough. For the event, urine should preferably be light yellow. If the urine is dark yellow, you have not drunk enough.

5. No salt tablets
In earlier years, salt tablets were sometimes recommended on hot days, but we have left those days behind. It is true that sweat contains salt, but using salt tablets is similar to drinking salt water: it only makes you more thirsty. Drink plenty of fluids and supplement the salt loss with the salt in your diet.

6. Adjust your pace
You may have trained for a new personal best, but you would do well to adjust your pace in warm conditions. This applies to everyone, including young and fit participants. Start carefully and control your pace; the adrenaline at the start makes it easy to start too fast. Walk your own pace and avoid big tempo changes during your race.

7. Make use of a Red Cross post
On the Dam tot Damloop course, you will find a Red Cross care station every 500 metres. You can go here if you do not feel well or are bothered by something else.

Should you recognise any of the symptoms of heatstroke as described above, stop immediately and seek help at a Red Cross post. Cooling baths led by doctors are also located 575 metres before the finish and after the finish line. It is also possible that the runner does not recognise the symptoms in himself; so also look at your fellow runners. See that they are swaddling? Take them to the side and have them lie flat in the shade and ask for help.

8. Clothing
To get rid of excess body heat properly, the right choice of clothing is crucial. Therefore, make sure you don't skimp on clothing but use high-quality clothing. The following tips will come in handy:

  • Don't dress too warm and choose clothes that minimise the evaporation of sweat. So use 'breathable' clothing;
  • On the day of the event, don't expose yourself too much to heat - so no hot clothes;
  • White clothing has the best reflection of heat from the environment, unlike black clothing. White clothing is therefore preferred;
  • Protect your head and neck when exposure to direct sunlight is unavoidable (breathable headgear);
  • Preferably use sunglasses to protect your eyes from bright sunlight.
After the event, take off your sweaty clothes as soon as possible and put on clean, dry clothes. This is important because the moisture in your sportswear cools down quickly and therefore your muscles can also cool down quickly.

9. Risk of recurrence
People who have had heat problems before have an increased risk of recurrence. If you are someone who has experienced this, be extra careful when exercising on hot days. In general, children, the elderly, people with underlying diseases (such as cardiovascular disease, lung disease or taking medication for mental illness) and less fit people (such as overweight / BMI above 25) are always at increased risk of heat disorders. They should better avoid situations of intense and prolonged exertion in heat.

10. Acclimatisation
When preparing for the TCS Amsterdam Marathon, try training on a hot day. This will help you learn how your body reacts to the heat and what signals it gives. It also allows your body to get used to exercising in warm conditions (acclimatisation) so that it is better prepared for possible heat during the TCS Amsterdam Marathon.

11. Train sufficiently
Prepare sufficiently and make sure you are fit for the start.

Tips from the Red Cross

The Red Cross conducted a survey among Dutch athletes and concluded that to prevent possible overheating, body signals should not be ignored. Read some advice and results of this survey on their website.
Thermo clinics
Become aware of your core temperature when exercising. To measure is to know, our body temperature fluctuates around 37 degrees Celsius. But during strenuous exercise, especially in warm conditions, that temperature can rise considerably. Exposure to low temperatures, such as when swimming in (ice) cold water, also has a major impact on our body's heat management. Especially for (endurance) athletes, it is important to be aware of this. Overheating and hypothermia can have major consequences for performance and health.

It can be an educational experience to measure your own internal body temperature (your core temperature), for example during a 10-kilometre run, during an hour of spinning at the gym or during and especially after winter swimming in open water. This can be done with an ingestible capsule from myTemp, which regularly transmits internal body temperature from the stomach or intestines, which can be read on a smartphone. You'll be amazed at your body's thermoregulation and how your core temperature affects your performance. Such a reading can help make you aware of the course of your core temperature during exercise and take the right measures to prevent overheating or hypothermia and maximise your performance. Many top athletes have gone before you in preparation for major sporting events such as the Olympics.

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