When is the best time to exercise in the heat?
You don't have to give up on your routine as the temperature climbs, says this expert - it's just about staying prepared
The sun is a welcome addition to our exercise routines come summer - but the novelty of a sunny run or hike can quickly wear off as the temperature climbs. With heatwaves and record-breaking temperatures already this year, it’s important to know the best time to exercise in the heat for the weeks ahead.
Obviously, if you don’t like the heat and would rather be inside, then you can exercise in an air-conditioned gym or studio at any time of day. A good swimming workout is another way to stay cool. However, if you enjoy running, hiking, cycling, or a garden strength training workout, it makes sense to choose the coolest times of day. In the peak of the summer, this is before 10 am and after 5 pm, but the earlier (or later) you can go, the better.
The body reacts differently in the heat, making exercise above 20°C degrees feel harder, even if you're doing the same workout you did in the cooler months. As the temperature climbs, blood vessels dilate to push blood towards the surface of the skin to cool it down, which means there is less in the muscles. This means your heart has to work harder and beat faster.
You also naturally sweat more, which is the body's way of cooling down. However, important micronutrients called electrolytes are lost in sweat, and if they aren't replenished (through hydrating foods or electrolyte supplements), it can lead to lower blood volume, triggering symptoms like fatigue, rapid heart rate, and dizziness that extend beyond your workout.
As well as checking the day's top temperature, you should check the heat index. This indicates how humid it can be, which can be more of a problem than the warmth and can leave you sticky and sweaty before you've even pulled on your running shoes.
With that in mind, Brian Maiorano, coach liaison for sports-tech company CORE, has some tips for exercising in the heat. “When the weather begins to really heat up, these are the best ways to train during a heatwave, and to really stay safe,” he says.
- Don’t be afraid to sweat: You can gradually adapt to the heat within 4 to 5 days by raising your core temperature in a controlled way. Top athletes call this ‘heat training’, and it’s very effective if you’re careful to not overcook yourself.
- Stay hydrated: As well as drinking water, you can douse your head and torso in it to stay cool.
- Lower your intensity during the heat: Monitor your heart rate and stick to zone 2 if you're exercising in the heat. This is 60 to 70% of your maximum heart rate (220 minus your age), and stop at any signs of dizziness, nausea, or headache.
- Choose when to do your most vigorous training: During intense sessions, you don’t want the additional stress of heat, so Brian recommends doing it in climate-controlled conditions (like switching your run to a treadmill workout) or choosing the best time to exercise in the heat.
- Don’t spend the whole day in an air-conditioned room: “Too much time enjoying the cool air can make you miserable when you are exposed to heat,” says Brian.
