How to exercise safely in the heat

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Sarah Griffiths, Lead Behavioural Insights Advisor, Bupa UK
27 July 2022
Next review due July 2025

Exercise has many health benefits, such as giving you more energy and better sleep. But what about when the temperature rises? Is it still safe for you to work out when it’s warm outside? Here I’ll explain what happens to your body when you exercise in hot weather, as well as how to exercise safely in the heat.

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What happens to your body when you exercise in hot weather?

Exercise causes your core body temperature to rise, however warm it is outside. But when you exercise in hot weather, your body needs to work extra hard. When this happens, your heart beats faster than it would in cooler temperatures. This is because it is working harder to send blood towards your skin to try and keep you cool.

Also, when you exercise in the heat, you sweat more than usual as your body tries to cool you down. When it’s very warm or humid, it’s harder for your sweat to evaporate into the environment. This can cause your temperature to increase even more, and if you don’t replace the fluids you’ve lost you can become dehydrated.

You may still be able to exercise in the heat if you make a few changes to when and how you work out.

How to exercise in the heat

Checking local weather forecasts and government guidelines can help you to prepare for hotter weather. When it’s hot outside, it may be safer to exercise early in the morning or later in the evening when the temperature is lower. If you’re not used to exercising in the heat then ease into exercise by starting at a lower intensity and taking more breaks than usual.

Other tips include:

  • Reduce the duration of your exercise – your body will be working harder than usual so you might feel tired more quickly, even if you’re used to regular exercise. Reducing the length of time you work out for can also lower your risk of experiencing any heat-related illnesses
  • Stay hydrated – if you are working at a high intensity, such as running or doing high-intensity interval training (HIIT) style sessions, then consider using electrolyte drinks or tablets to rehydrate you and replace any lost minerals such as potassium and sodium
  • If you’re working at a lower intensity, make sure you drink plenty of water before exercising, and drink little and often during exercise – which will reduce digestive issues too
  • Wear lightweight, light-coloured clothing which won’t absorb the heat, and will help your sweat to evaporate
  • Ideally, wear a hat and sunglasses to reduce your sun exposure, and don’t forget the sun cream too

You are more likely to experience heat stress if you’re elderly, pregnant or have other underlying health conditions. If you do have a medical condition which might make working out in the sun dangerous, then please see a doctor to get personalised advice before exercising in hot weather.

Signs of heat-related illness

It’s normal to feel warm, sweaty and a bit more out of breath when you are exercising in the heat. But there are some key signs to look out for to reduce your risk of health issues such as heat exhaustion and heatstroke. These include:

  • Muscle cramps
  • Feeling or being sick
  • Weakness and fatigue
  • Headaches
  • Excessive sweating
  • Feeling dizzy or faint
  • Visual problems

If you notice any of these symptoms, then you should stop exercising and find some shade. Drink fluids and apply cool water to your skin. If you feel very unwell then get immediate medical attention as heatstroke can be serious if not treated quickly.

Alternatives to exercising in the heat

Sometimes, it might be too hot to exercise safely and enjoyably outside. This may be the case if there is an unusually high temperature, such as during a heat wave, or if you have gone to a hot and humid country on holiday.

Here, you might like to keep up with your exercise regime in a different way. Instead, you could try:

  • Exercising indoors if it is cool enough, by using an online video for guidance
  • Using the gym facilities where you are staying, which might be air conditioned
  • Swimming at an indoor pool
  • Using resistance bands to do a range of strength-building exercises

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Dr Sarah Griffiths (she/her)
Sarah Griffiths, Lead Behavioural Insights Advisor, Bupa UK

    • Physical activity. Department of Health and Social care., edited 14 August 2014
    • Regular Exercise Plays A Consistent And Significant Role In Reducing Fatigue ScienceDaily. University of Georgia., 8 November 2006
    • Exercise and sleep. The Sleep Foundation., updated May 2022
    • Takeda R, and Okezaki, K. Body temperature regulation during exercise and hyperthermia in diabetes. Diabetes and its complications, 2018. 10.5772/intechopen.74063
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    • Heat related illness. Patient professional., accessed 19 July 2022
    • Personal correspondence with Dr Sarah Griffiths, Lead Behavioural Insights Advisor, BGUK
    • Seven tips for exercising safely during a heatwave. The conversation., published 18 July 2022

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