25/06/2017 - 14:13


Looking ahead, with the warmest days of the year still to come, and a potential heat wave on its way, the question arises whether you can keep working out safely during extreme heat. The answer is simple: yes, you can, but only if you take the right precautions: adapt your workouts, and carefully listen to your body. If you fail to do this, it could very well be dangerous. This article tells you what to look out for, and how to responsibly work out in extreme temperatures.  


In principle, your body is very well capable of protecting itself against overheating. However, if you decide to exercise in warm weather or during a heat wave, there is a limit to what your body can do. Intensive workouts can be dangerous to anyone when temperatures rise above 28°C. In untrained people, problems can already occur at 25°. There are some heat-related conditions, with progressive symptoms:

  • Heat cramps

Heat cramps occur mostly in people who sweat a lot, because cramps are caused by dehydration and a lack of minerals. When you sweat profusely, you lose both fluids and sodium (salt). Heat cramps occur in the muscles of the legs, arms, stomach and back. Apart from sweating, you will notice a reddening of the skin, thirst, and of course aching legs, arms, stomach or back.

Heat cramps can be prevented by drinking more and taking additional sodium (eating more salt than usual). In warm weather, you should consume about half a litre to a litre of water extra (in addition to your regular fluid intake). You can also drink isotonic sports drinks.

  • Hyperthermia

When the blood vessels stop working due to serious dehydration, this causes hyperthermia. Profuse sweating will cause dehydration, which leads to a lower blood volume. The body's temperature control system still functions, but the body is unable to release enough heat because there is not enough blood to transport the heat to the skin. Hyperthermia occurs more often in untrained people.

  • Heat stroke

A heat stroke happens when the body's temperature control has failed. In case of a heat stroke, the core temperature of the body rises to more than 40°C. When this happens, the mental status of the person changes, because the neural tissue in the brain is very sensitive to extreme heat. Rapid intervention is required, because the heat stroke could cause the patient to lapse into a coma, and potentially die. The victim should be cooled down as quickly as possible, preferably by immersion in a bath filled with (ice) cold water.


To work out or not to work out during a heat wave

Whether your body can cool down by perspiration is largely determined, apart from the intake of fluids, by the wind. A lot of wind will ensure the evaporation of sweat. It is better not to work out too intensively when there is little wind, if:

  • It is more than 30°C in the shade
  • It is more than 28°C in the sun (temperature measured in the shade)

High relative humidity causes the sweat to evaporate much more slowly. At a temperature of 25°C that is not a problem, but at 30°C, the temperature seems higher when the relative humidity reaches more than 70 percent. At 35°C, the perceived temperature rapidly increases when the relative humidity exceeds 40 percent.

The heat index as a guide

The calculation of the heat index takes into account both the temperature and the relative humidity. The higher the temperature, and the more humidity in the air, the higher the heat index will be. A heat index of more than 39°C is acutely dangerous for people who exert themselves. This heat index starts at a temperature of over 35°C in the shade, combined with a relative humidity of over 50 percent. Wind is not a relevant factor for the heat index calculations.

The Wet-Bulb Globe Temperature (WBTG) is a guideline applied by sports institutes to determine whether a competition can go ahead. The WBTG is calculated based on temperature, relative humidity, wind speed and solar radiation. The WBTG is applied, among others, by the Women’s Tennis Association (WTA) and the International Tennis Federation (ITF); their rules state that matches can be postponed in case of a WBGT of more than 28°C.


How to prevent overheating

Prevention is better than cure. When a heat wave is coming, and you want to continue your training, make sure you implement the following precautions.

  • Train in the morning or the evening.

If you want, you can always train at night. In any case, do not train during the hottest hours of the day, between 12 and 16h. Your body’s ability to process the heat depends on the amount of sun, the air temperature, the wind speed and the relative humidity. When the sun is high in the sky, it radiates much more heat than when it is lower.

  • Drink plenty of fluids

Try to take in as many fluids as you expect to lose through sweating. This is difficult to assess, but you could weigh yourself before and after a workout, to get an idea of the amount you lose. During strenuous efforts, the body could sweat out more than a litre of fluids per square metre of the body surface. A person who weighs between 50 and 75 kilos could lose 1.6 to 2 litres of sweat per hour. The maximum amount of sweat could amount to some 10 to 15 litres, but that is only possible if you take in plenty of fluids.


Remember to drink before you get thirsty. Once you get thirsty, you're already too late.

  • Wear little clothing

Wear as few items of clothing as possible. Clothing increases the heat, so less is better. You should also select light-coloured clothing that reflects a lot of the heat. A white cap and sunglasses can also help a lot.

The downside to exercising outdoors is that you are more vulnerable to sunrays. In that case, you should use plenty of sunscreen, preferably a cream that protects against both types of UV rays, UVA and UVB, with a high sun protection factor.

  • Select a good location

If you have the option, you should select a suitable location. Working out in de the shade helps. If you have a gym with air-conditioning, that is even better. If you run outdoors, you should remember that unpaved roads radiate less heat that asphalt, for instance. And this might be a good time to go swimming in a pool, instead of running.

  • Wear a heart rate monitor when performing cardio exercises

During a heat wave, your heart rate during a workout will be higher than usual. This is partly due to the temperature, but also a result of the relative humidity. Because the body temperature rises, the blood vessels in your arms and legs get wider. A part of the total blood volume is transported to the limbs. This means that there is less blood in the heart, and every heart beat pumps around a smaller amount of blood. The heartbeat rises, trying to compensate and ensuring that the amount of blood that is pumped around, remains the same. The same effect occurs when you don’t drink enough fluids.


The use of a heart rate monitor allows you to keep a close eye on your heart rate. This tells you right away when you have to slow down. 

  • Use menthol spray

Pouring water on your shirt can help you cool down. Even more effective is the use of menthol spray; at any rate, it is more comfortable. This spray is usually applied to bruises and injuries, but it also works great when you put it on your shirt.

  • Take it easy

Whether you do a cardio session or power training, don't try to break any personal records on those very hot days. Instead, try to take it a little easy. Don't run too hard or far, try to use fewer weights, and in all cases: listen to your body!


Use supplements

Because exercising during a heat wave causes you to lose a lot of fluids and minerals through profuse perspiration, it is better to drink isotonic sports drinks than water. Isotonic drinks are absorbed more quickly than water, and at the same time restore the minerals that were excreted through the perspiration process. The sports drinks also contain carbohydrates that offer a little additional energy.

Take SynaVit to supplement all vitamins and minerals. This multi-nutrient preparation contains all required vitamins and minerals, in the right amounts, and also contains grape seed, green tea and Q10 co-enzyme. SynaVit's most important strength is the synergy between the different nutrients.

SynTsize Recovery is the ideal product to help with your complete recovery. This is an ideal post-workout shake containing the right mixture of fast carbohydrates and proteins, as well as some key amino acids and supporting substances. The two hours right after the workout are called the ‘Anabolic Window’. During this time, the carbohydrates you've ingested are completely processed to supplement the muscle glycogen.


No need to stop working out during the next heat wave. Read the article again, take the right precautions, drink plenty of fluids, take supplements, take it easy and listen to your body! 



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