Love exercising outdoors but don’t like the way heat waves and out-of-control humidity can turn a refreshing long run into a sweat-drenched experience? Me too. Here’s what you need to know about overheating and how to prevent it.

But first it’s good to know why and how we overheat…

Physical exercise causes the body to generate heat, which in turn raises our core body temperature. The harder you exercise, the more thermal heat your body will produce. Thankfully our sweat glands are designed to cool the body down by pumping water through the skin to evaporate into the air, taking a heap of body heat with it. Usually, as the sweat evaporates off the body, the core temperature will remain at an acceptable level. But, unfortunately, it doesn’t always work that way.

If a person’s core body temperature rises to about 40°C, the consequences can be dire. The body overheats and puts strain on the heart, pumping less blood to vital organs and bringing less of the rising core body heat to the skin’s surface. The strain that results causes increased heart rate and blood pressure, your performance will be compromised, and symptoms such as dizziness, muscle cramps and disorientation are common.

Just how hot and bothered you get on the inside depends on a number of factors. When the outside temperature passes 37°C, for example, your body begins to absorb heat from the environment, on top of the heat you’re absorbing from the sun. Humidity adds an extra whammy. High humidity makes evaporation – the body’s best cooling mechanism – less efficient, so sweat drips off the body instead of evaporating and cooling it.

Whether you exercise on grass or on the road also has an impact. Darker surfaces like asphalt draw more heat from the sun and are transmitted to the body.

Finally, how acclimatised you are to exercising in hot weather counts, too. It’s much harder for the body to cope with heat if it’s not used to it.

How to prevent overheating while exercising?

  • Stay well hydrated at all times to maintain quality performance in workouts and competition. As water content drops, less is left for sweat, meaning less sweating and less cooling. Water is always the best fluid of choice when you’re exercising for less than one hour, but fluids with electrolytes when exercising longer than one hour is crucial.
  • Always wear light-coloured, loose-fitting clothing.
  • If it’s unavoidable and you do have to work out or compete in the heat, give your body time to acclimatise to the higher temperatures. Plan on shorter and easier workouts for at least two weeks, in the cooler part of the day, and slowly build up to intense workouts at the hottest times of the day.



Kathleen Alleaume is an accredited exercise physiologist and nutritionist and founder of The Right Balance