How to exercise safely in a heatwave: a South African summer guide
South African summers regularly push past 35°C inland, and heatwave warnings from the South African Weather Service are now a familiar part of the season. You don't have to stop exercising when it's hot, but you do have to change how you do it. Heat illness can come on quickly and can be life-threatening. Here's how to keep training safely, and the warning signs that mean stop.
Why heat makes exercise harder
Working muscles produce heat, and your body gets rid of it mainly by sweating. In hot weather, and even more in humid weather, sweat evaporates less well, so your core temperature climbs faster. Your heart has to pump blood to your skin to cool you and to your muscles to fuel them, so it beats faster at the same effort. That's why a run that feels easy in winter can feel brutal in January.
7 ways to train safely in the heat
- Move your session. Exercise early in the morning or after sunset. Avoid the hottest part of the day, roughly 11 am to 4 pm.
- Check the forecast and heat warnings. On a heatwave day, swap your outdoor session for something indoors, in the shade, or in the pool.
- Drop the intensity. Go slower, shorten the session, and take more breaks. Judge effort by how you feel, not by your usual pace.
- Drink before, during and after. Start well hydrated, sip regularly, and keep your drink cool. For sessions over an hour with heavy sweating, a drink with electrolytes helps replace the salt you lose. Our hydration guide covers how much is enough.
- Dress for it. Loose, light-coloured, breathable clothing, a peaked cap or hat, and water-resistant sunscreen of SPF 30 or higher.
- Get used to the heat gradually. Your body adapts to heat over about 10 to 14 days of shorter, easier sessions. Early-summer heat and the first hot days after a cool spell are the riskiest.
- Don't train alone in extreme heat, and tell someone your route if you do.
Who needs to be extra careful
- Adults over 65, young children, and anyone pregnant.
- People with heart, lung or kidney conditions, diabetes, or high blood pressure.
- Anyone taking medicines that affect fluid or temperature control, such as diuretics (water tablets), some blood pressure medicines, antihistamines and some antidepressants. Ask your pharmacist if yours is 1 of them.
- Anyone who is unwell, has had a stomach bug, or has been drinking alcohol.
The warning signs
Heat exhaustion: stop, cool down, drink. Heavy sweating, cool clammy skin, dizziness, headache, nausea, cramps, weakness, a fast pulse. Get into the shade, lie down with your legs raised, loosen clothing, sip water and sponge yourself with cool water. If you don't feel better within 30 minutes, get medical help.
Heat stroke is an emergency
Confusion, slurred speech, unusual behaviour, collapse, a seizure, or hot skin with a very high temperature, whether sweating or not. Call 10177 (ambulance) or 112 from a mobile straight away, and cool the person as fast as you can while you wait: shade, remove extra clothing, cold water over the skin and fanning, ice packs at the neck, armpits and groin.
Where collagen fits
Collagen won't protect you from the heat, and nothing you can take replaces the steps above. What it can do is support your joints and tendons through regular training, which is what Active is made for. We go through the research in collagen and sport performance and collagen for joint health. A scoop dissolves in a cold drink or a post-workout smoothie.
Active collagen for training
Bioactive collagen peptides for people who train, from the range we've supplied since 2016. Mixes into cold drinks. See Active → Free delivery on orders over R800.
Frequently asked questions
How hot is too hot to exercise outside?
There's no single number, because humidity, sun, wind and your fitness all matter. On days the Weather Service issues a heatwave or high-temperature warning for your area, move your session indoors or to the cooler ends of the day.
Is it safe to swim in a heatwave?
Swimming is 1 of the best options, because the water cools you. Still drink water, use sunscreen, and avoid the midday sun.
Do I need a sports drink?
For most sessions under an hour, water is enough. For longer or very sweaty sessions, something with electrolytes helps. Many sports drinks are high in sugar, so check the label.
Can I drink too much water?
Yes. Drinking very large amounts of plain water during long events, without replacing salt, can dangerously dilute the sodium in your blood. Drink to thirst and include electrolytes on long, sweaty days.
The sources
- World Health Organization. Heat and health: fact sheet. View →
- South African Weather Service: forecasts and warnings. View →
Find out more
- 6 health benefits of staying hydrated
- Collagen and sport performance
- How to manage muscle pain after exercise
- Bicarbonate of soda and athletic performance
This article is general information, not medical advice. If you have a heart, lung or kidney condition, diabetes, or take regular medicine, ask your doctor how to exercise safely in hot weather.
About the author
Candy Hamilton is the owner of Health Nut, which has supplied collagen to South African homes and health shops since 2016. She holds a Certificate in Human Nutrition from Health Academy Australia (2020) and writes the research summaries on this site. Every study cited is linked so you can read it yourself. More about Health Nut →
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