Exercising in the heat: how to adjust your workouts as spring warms up

Spring has barely started and the heat has already arrived in parts of Australia. Sydney sweltered earlier this week before temperatures plunged 14 degrees the next day, the Top End has had heatwave conditions, and the Bureau of Meteorology expects warmer than usual days and nights for most of the country through to December.

If you walk, run, ride or train outdoors, that changes things. The same route at the same pace can feel much harder on a hot morning, and that is not a sign you have lost fitness. It is your body working to stay cool.

Here is what heat does to exercise, practical ways to adjust, when to stop, and how the Thrive Health Band shows how your own body responds on warm days, so you can keep moving through summer.

What heat does to your body during exercise

When you exercise, your muscles make heat. On a cool day it escapes easily. On a hot or humid day, your body works harder to get rid of it: more blood goes to your skin, you sweat more, and your heart beats faster to keep everything supplied.

That is why your heart rate is usually higher in the heat at the same pace, and why an easy jog can feel like a hard one. Humidity makes it tougher again, because sweat does not evaporate as well.

The good news is that your body adapts. Over one to two weeks of regular, sensible exercise in warmer weather, you tend to start sweating earlier and your heart rate settles a little at the same effort. That is why the first hot days of spring often feel worse than the same temperature in February.

How to adjust your workouts

Go early or late. Early morning is usually the coolest part of the day. Evenings can work too, though pavements and buildings hold heat.
Slow down and go by effort. Expect to run or ride slower on hot days. Go by how hard it feels, or by heart rate, rather than chasing your usual pace. Our article on heart rate zones explains how.
Ease in over the first couple of weeks. Start with shorter sessions and build up as you adapt.
Drink water before, during and after. For longer sessions in the heat, take water with you and plan refills.
Dress light and find shade. Wear loose, light-coloured gear, a hat and sunscreen, and choose shady routes or an indoor option on very hot days.
Move the hard session. On the hottest days, swap intervals for an easy walk, a swim or an indoor workout. Keeping the habit going matters more than one big effort.
Look after your sleep. Hot nights can cut into recovery. Our article on warm nights and summer sleep has ideas.

Take extra care if you are older, pregnant, new to exercise, or have a heart condition or other health condition, and check with your GP about what suits you.

When to stop

Listen to your body. Health authorities such as NSW Health advise stopping, resting somewhere cool and sipping water if you feel dizzy, faint, sick, unusually tired, very thirsty or get a headache or muscle cramps. If you feel confused, have hot, dry skin or stop sweating or feel very unwell, call 000 or seek medical help straight away.

How Thrive shows your response to the heat

The Band has no screen, so there is nothing to squint at mid-run. Wear it and get on with your day, and the Thrive by Optihealth app shows the picture afterwards.

Heart rate during workouts. See your heart rate and zones for each workout, so you can compare a hot morning with a cooler one at the same pace.
Heart rate recovery. Thrive looks at how quickly your heart rate comes down in the minutes after a workout, a useful sign of how hard a session was for you.
Temperature. Thrive tracks your temperature trends alongside heart rate, so warm days and hot nights sit in the same picture as your training.
Recovery insights. After a big session, Thrive gives an estimate of how long until you are back to your usual, such as "you need 5 hours rest", so you can plan an easier day.
Today's Vitality and Today's Load. Today's Vitality brings Sleep & Recovery, Heart & Nervous System, Today's Load and Mind & Mood together, so you can see how a hot week is landing.
Ask Thrive. Try "How did my heart rate on my usual run compare this week with last month?" or "How long did I take to recover after my hot weekend ride?"

Thrive also learns what is usual for you across nine areas of your health, from what the Band measures and what you log, and keeps track right across your health, including sleep, stress and mood, meals and Food Fit, blood tests, medications and supplements and your medical history. The Band runs for up to 14 days on a charge, so it keeps up with a busy summer.

If you train with someone, Thrive Loops lets you share selected information with a participating trainer, health professional or someone you trust. You decide what to share and with whom, and you can change or revoke access at any time.

When to talk to your GP

If hot weather regularly leaves you feeling unwell during or after exercise, or you have a health condition or take medications that may affect how you handle heat, talk with your GP before summer. Thrive isn't a diagnosis, but Ask Thrive can help you get ready by lining up your recent workouts, heart rate and how you have been feeling. Here is how to use Ask Thrive before a GP appointment.

Before you buy

You'll need a compatible iPhone or Android phone, because the Thrive app is on the Apple App Store and Google Play, in Australia and eight other countries. The app stores are only for downloading the app, though; they aren't where you buy the Band or a Plan. You can buy at thrivehealthband.com, or at a participating World Gym Australia location or health and wellness clinic.

The Thrive Health Band is A$660 for the first year under the launch offer. That includes the Band, which is yours to keep, and 12 months of the Thrive by Optihealth app, My Health on the web, Health Fingerprint, Ask Thrive, Thrive Loops and your data, paid once upfront. Prices are in AUD and include GST. Free Australia-wide shipping during the launch offer (usually A$14.99).

Nothing renews automatically. After your first year, you can get a new band plus 12 more months for A$660, or keep your band and renew the Thrive Connected Plan for A$240 a year, or A$29 a month with no lock-in.

You're also covered by a 12-month Thrive Care Warranty, and consumer guarantees under Australian Consumer Law always apply. See Returns if something is wrong with your purchase.

Common questions

Why is my heart rate higher when I exercise in the heat?

Your body sends more blood to your skin to release heat, so your heart works harder to keep up at the same pace.

How long does it take to get used to exercising in the heat?

Your body usually starts to adapt over one to two weeks of regular, sensible exercise in warmer weather.

Can Thrive show how the heat affects my workouts?

Yes. Thrive shows your heart rate, zones and recovery for each workout alongside temperature trends, and Ask Thrive can compare hot and cooler days.

For more answers, see Questions.