Media Release

January 29 2009

Exercise precaution to avoid heat illness

Take precaution when exercising in hot weather Active people must take precautions if they plan to exercise during the current heatwave – or risk heat illness or heat stroke, says UniSA Exercise Scientist Dr Grant Tomkinson.

Dr Tomkinson says while exercise is obviously beneficial to health, the State’s current scorching temperatures mean people need to follow important precautions.

And if you’re not active already, now is definitely not the time to start.

“There are some commonsense precautions you can take, such as exercising in the coolest part of the day, drinking plenty of cold water, and minimising the duration and intensity of your session,” Dr Tomkinson said.

“If you are a regular exerciser, don’t do more than you normally would; definitely don’t ramp up the intensity.

“And if you’re a new exerciser – say it was your New Year’s resolution to start an exercise program in 2009 and you’re thinking of going for a 20 minute jog – the message is just don’t do it. Wait until the heat wave is over and then start slowly.”

Dr Tomkinson said the most important thing people should do during the heatwave is listen to their body.

“If your body is telling you to stop, then stop, because exercise is relatively harder in the heat than in milder temperatures” he said.

“Going to the gym, where the internal environment is air conditioned with circulating air, won’t be too bad, but anyone choosing to run outside – especially in the middle of the day or early evening – will really suffer.

“In extreme hot weather we have a reduced ability to lose heat from our body. As soon as our internal body temperature increases by a couple of degrees, our performance declines, and if our body temperature increases to 40 or 41 degrees, then we’re in danger of heat illness or heat stroke.

“Parents should also be aware that children may be at greater risk as they have a lower tolerance to prolonged exercise in the heat, compared to adults.”

Dr Tomkinson said precautions for safe exercise include:

Exercise in the coolest part of the day – early in the morning or late evening.
Minimise the intensity and duration of your session.
Expose as much skin to the environment as possible, as this encourages evaporation of sweat and allows the body to cool. Wear plenty of sunscreen.
Take frequent breaks and listen to your body.
Drink plenty of cold water. Consume half to one litre of water at least 1-2 hours before the session, then at least a cup of water every 10-15 minutes during the session. Drink plenty after the session.
A more scientific approach to hydration is to weigh yourself before and after the session. After the session, put back 150 per cent of fluids you have lost. For example, if you lost half a kilogram in weight during the session, drink at least 750ml after the session.
Monitor urine colour. If you’re hydrated, urine is clear. If you’re dehydrated, it’s dark yellow.
Consider drinking sports drinks to replace lost electrolytes, although water will normally be sufficient. Alternatively, because flavoured drinks are generally preferred, you could try adding some flavour to your water.