Hi, how are you.

He we are again … this month I thought it would be useful to talk about physical exercise and heat.

We all know that during this period of extreme heat there are certain times of the day when it´s not suitable to exercise. The best time to exercise is first thing in the morning or during the evening, making sure to hydrate before, during and after your exercise and to wear light comfortable clothing. In the past it was believed that the more we sweat the more weight we lose and so people wrapped their abdominal area in plastic or ran wearing heavy clothing but this is totally mistaken as what happens is the central temperature is raised and as soon as we drink water, any weight lost is regained.


Sweating is a physiological response that reduces an increase in the body´s core temperature by placing water droplets on the skin to evaporate so it´s important to drink fluids to compensate for that loss of water.

Another common mistake we sometimes make is to wait until we feel thirsty to have a drink. If we feel thirsty, we are already dehydrated! The sensation of thirst is a signal from the brain that informs us of dehydration.   It is important to hydrate before starting to exercise even though we don´t feel thirsty … if we wait until we feel thirsty and already have a fluid deficit it is difficult to rehydrate sufficiently. It´s also worth remembering that the sensation of being thirsty disappears well before we have replenished all the liquid lost, especially when we are drinking drinks low in sodium, such as water – thirst diminishes through a dilution of sodium in the blood. Also, as soon as the first drop of liquid wets the mouth, its nerves send signals to the brain to lessen the sensation of thirst.

Female athlete drinking water.

The importance of flavour and electrolytes One of the things that most impacts on the amount of fluid consumed during exercise is the type of drink. Many studies have found that if the drink has a flavour, people voluntarily drink much more than if they only drink water. If as well as having a nice taste, the drink contains electrolytes (like sodium), it stimulates further consumption of the drink. So look for drinks that improve your hydration and if you decide to drink just water, remember that the sensation of thirst will disappear more rapidly.

Exercising in excessive heat can put your health at risk, for example:

  • Cramps – muscle cramps, usually in the legs or in the stomach can be the first sign of overheating
  • Heat exhaustion – profuse sweating, cold, clammy skin, nausea and vomiting
  • Heatstroke – when the body temperature rises above 40C

Children, the elderly and overweight people are at higher risk of experiencing these problems, as are people taking certain medications and those with heart problems. However, everybody needs to take care – even an athlete in great physical shape can suffer from heatstroke or sunstroke!

Advice on exercising during the summer:

  • Drink a lot .. even if you don´t feel thirsty.
  • Don´t drink alcohol, caffeine or sugary fizzy drinks as these can have a diuretic effect and your body can actually lose fluid.
  • Water is the best option for less intense training. If you are planning to exercise for a couple of hours, an energy drink or one with electrolytes is better as these drinks replenish the salts and minerals. Choose the lower calorie ones that have less sugar.
  • Ensure that your drink is chilled but not overly cold as drinks that are too cold can cause stomachache.
  • Don´t drink effervescent salts as these can increase your risk of dehydration.
  • Rest frequently in the shade.

Signs of heat exhaustion:

It´s important to recognize the early signs of heat exhaustion

  • Profuse sweating
  • Tiredness
  • Thirst
  • Muscle cramps

Advanced signs can include:

  • Weakness
  • Dizziness
  • Headache
  • Cold, clammy skin
  • Dark coloured urine

Signs of sunstroke can include 

  • Fever (over 104F or 40C)
  • Red, hot, dry skin
  • Rapid, short breaths
  • Weak, fast pulse
  • Irrational behaviour
  • Extreme confusion
  • Fits
  • Loss of consciousness

As soon as you notice the first signs of heatstroke or sunstroke, get out of the heat or sun immediately, remove any unnecessary layers of clothing and drink water.

I hope this advice has been helpful and that by putting it into practice, you continue to take care when exercising correctly.

Until next time!