Is it safe to exercise in hot weather? The experts weigh in

With a mini-heatwave in full flow, it’s more important than ever to look after your wellbeing, especially if you’re working out. Some experts say that in extreme temperatures, you might want to forgo your fitness routine altogether because exercising in the heat will raise your temperature and potentially place extra stress on your body. However, it is possible to work out safely, if you know what you’re doing and how to take care of your health.

The type of exercise you choose to do, the air temperature and the level of humidity can all increase your core body temperature and mean that your body has to work harder to cool off. There’s also the added risk of fatigue, longer recovery times and heatstroke, so knowing how to stay safe is paramount.

If you’re not willing to skip leg day just because the temperature is rising, there are a few things to consider and some useful swaps and adjustments you can make to ensure your workout is safe and that you’re staying as cool and hydrated as possible. We turned to Brian Maiorano, coach liaison for Core , the smart body temperature monitor and Helen O’Leary, physiotherapist and director of Complete Pilates for their expert tips on how to exercise in hot weather. Here’s what they had to say.

Is it safe to exercise in hot weather?

“You can still exercise in hot weather but it is important to consider a few things,” says O’Leary. “Exercising in the heat can increase your risk of heat exhaustion. This is when the body overheats in response to external factors, like temperature. It can happen to anyone and is common in athletes. However, it can also happen when you are sitting in a hot car!”

“The higher the temperature, the greater the risk of dehydration or heat stroke. Is there a lot of humidity? If the answer is yes this means that there is more water in the air which will make it more difficult for your body to lose heat.”

It’s also vital to make sure you have the right gear. Wearing flexible, lightweight and breathable fabrics is best in hot weather and a looser fit can be useful too as it allows your body to lose water. If you’re wearing something that fits close to the skin, opt for a sweat-wicking fabric , ideally in a lighter colour that will reflect heat and light, rather than absorb it.

Read more: I add electrolyte sachets to my water every day, here’s why it’s a must

You might also want to consider wearing other protective gear, such as a hat and sunglasses and make sure you’re wearing sunscreen too. Generally, if you’re exercising outdoors you’ll need to be prepared, whatever the weather, but it’s especially important to remember this in hot weather when you’ll be sweating a lot more than usual.

Intense heat will cause the body to send more blood to the skin to stay cool and regulate sweat. This transfers blood away from the muscles more quickly than usual. “Sweating is a necessary thermoregulator and the amount we sweat is linked to the amount of skin blood flow,” explains O’Leary.

Because of the higher skin blood flow, our heart will generally beat more. During exercise, the main challenge of the cardiovascular system is to provide enough blood flow to the skin for effective temperature regulation but also to provide sufficient blood flow to the muscles to support metabolism.

“How much we sweat is seriously variable and depends on the environment we are in, our clothing and the physical activity we are doing. For example, if humidity is high then it is harder for the body to sweat because there is already more water in the air. This means our sweat doesn’t easily evaporate.”

In normal activities, you’re likely to sweat out around one litre per hour but this can rise as soon as the body starts straining. The more you sweat, the more likely it is that you’ll become dehydrated so it’s essential to top up fluid in the body to avoid dehydration and to maintain blood flow volume. If you don’t you could start to feel unwell very quickly.

Stay hydrated

Drinking plenty of fluid while you’re exercising is key, but you also need to make sure you’re hydrating before and after a workout to replace the fluid you lose when you sweat. There are also a few health hacks you can try that will top up your hydration levels. “We all know the importance of hydration,” explains Maiorano. “But remember that doing things like dousing the head and torso with water is a great way to stay cool and replenish moisture.” You can also try replacing the salts and minerals lost through rapid sweat loss quickly by drinking electrolyte drinks , which contain a hit of those essential nutrients.

“The benefits of having near-optimal hydration are that it helps you maintain your mood, recover from exercise, perform well and have good heat transfer,” says O’Leary. She recommends the following formula to optimise your workouts and hydration levels.

• Before exercise: Drink around 5-10ml per kg of body weight around two to four hours prior to exercise.
• During exercise: You want to replenish the water lost. Take a few sips every 10 to 20 minutes but if you are excessively sweating you can drink a little more or try a sports drink.
• Post-exercise: drink and eat as you normally would. If you have lost more than 2% of your body weight before exercise from sweating and going to the toilet, drink around 1.5l for every 1kg lost. Make sure you also eat well.

Read more: How to stay hydrated in hot weather, according to experts

To avoid losing too much body fluid to sweat, Maiorano advises doing your most vigorous training during the coolest parts of the day, either first thing in the morning or in the evenings. Or moving indoors to climate-controlled conditions. Swapping that trail run or weights session outdoors for a class or an air-conditioned gym might help, especially if you usually train hard. “During intense sessions, you don’t want the additional stress of heat. However, don’t spend your days holed up in an air-conditioned room. Too much time enjoying the cool air can make you miserable when you are exposed to heat,” he says.

What are the best exercises to do in hot weather?

Maiorano advises that it’s best to lower your workout intensity during the heat. This might mean shortening your intervals, opting for low-intensity exercise like pilates and yoga over higher-intensity styles like HIIT and Crossfit and lowering the weight you lift.

“Monitor your heart rate and, ideally, your core body temperature. Keep both below safe thresholds, and stop at any signs of dizziness, nausea or headache. You can gradually adapt to the heat within for to five 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,” he says.

However if you live somewhere cold and are struck by a sudden change in temperature, it can take longer for your body to adjust. “It can take up to around two weeks for this to happen so be patient with yourself and listen to how you are feeling. This partly depends on your ability and fitness levels and there is no one size fits all,” explains O’Leary.

“On really hot days you can try things like stand-up paddle boarding , kayaking, surfing or swimming. All these help to keep you cool but will also help you stay fit and healthy. If you are a novice exerciser or have never exercised in the heat before, try doing more gentle workouts like Thai Chi or walking . You can also do some bodyweight beginners Pilates, Yoga or gym-based exercises. Try to keep the programme to the whole body rather than specific areas and let your body adapt.”

In hot weather, the most important adjustment to your workout will be your cool down. O’Leary advises giving yourself time for a five to 10-minute cool down at the end of your workout.

“For instance, if you are running then walk for five to 10 minutes at the end. This gives your body time to take your heart rate down slowly which will help your body temperature to cool. It should be active but at a lower intensity than your main workout. You might find this takes longer in the hot weather so schedule it into your workout. It also reduces the risk of suffering symptoms such as feeling faint or lightheaded after exercise in the heat. It is not advised to suddenly stop after a workout.”

The verdict: Working out in the heat

If you’re going to work out in hot weather, try to make adjustments to your routine so that you can stay safe and recover faster. Drink water and top up on electrolytes , wear loose clothing and lighter colours and try to avoid the sun in its hottest period, between 11am and 3pm. You can also follow Maiorano’s advice and sprinkle water over your skin or clothes and modify your exercise style to go easier on your body and avoid losing too much sweat.

O’Leary says “there is also some research that shows that having an alternating shower of hot and cold is better at regulating your body temperature after exercise than just having a cold shower. You might also want to try using a cooling moisturiser on your skin ( aftersun is good for this) or drink a menthol drink as menthol feels cooling. Some people find drinking a cup of tea actually helps them to feel cooler too.”

“Knowing your exercise level is really important. If you have never exercised before, going for a run in the hot midday sun is not a good idea. Instead, build up your tolerance slowly and remember things take time to adjust”