Training and racing in the heat – top tips for keeping your cool when the heat is on

The heat is on! But when the mercury soars, how can you minimise the impact of hot conditions on your performance? We share some top tips for training and racing in the heat, including some PRO insights from Lucy Charles-Barclay.

Writer & Long Course Triathlete
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When the mercury rises and the sun beats down, getting your training sessions done or performing at your best during a race can feel like a struggle. Heat and humidity can be energy sapping at rest, let alone while you’re putting in the miles.

Whether you’re trying to keep your training ticking over during a heatwave. Or the forecast is looking hot and spicy for your next race. We share some top tips for training and racing in hot conditions.

Why does working out in hot conditions feel so much harder?

If the struggle feels real when the weather hots up – rest assured, it’s not all in your head. Heat and humidity has a physiological impact on your ability to perform. Higher air temperature means that your core temperature becomes elevated a lot sooner when you start to exercise. Your body diverts blood supply away from the muscles and organs to the skin surface to prioritise cooling. This puts a higher strain on the cardiovascular system, and reduces your capacity for aerobic performance. Reduced blood flow to the muscles also decreases oxygen availability in the muscle fibres, speeding up your time to fatigue.

Heat also increases your sweat rate, meaning you’re losing electrolytes at a faster rate – which can have an impact on muscle contractions. And where you’ve got the double-whammy of heat and humidity, your sweat doesn’t evaporate as quickly so all that salt loss doesn’t even give you the desired cooling effect.

In practice, all of that physiological impact results in you experiencing a higher heart rate at lower intensities and an increased perception of effort. Making it harder physically and mentally to push yourself.

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How long does it take to adapt to the heat?

The good news is the body can adapt to the heat – and perform well. You only have to look at what the PROs are able to achieve at the IRONMAN World Championship in Kona or what ultrarunners can pull out of the bag at events like the Marathon des Sables. Our bodies are pretty good at responding to a stimulus and thinking “well, that was tough – let’s work some magic so it’s not quite so tough next time.”

Research has found that after 7-10 days of heat exposure, the body is able to adapt and respond. You’ll start sweating sooner, to maximise the cooling effect. But the body gets better at holding on to electrolytes, conserving salts. Your cardiovascular system gets more efficient at directing blood flow to the skin and muscles, helping to lower your heart rate. And your perceived effort and comfort levels in the heat also improve.

Triathlon cycling in the heat
The body starts to show good heat adaptation after 7-10 days of training in warm conditions.

This is why you’ll note that plenty of top level athletes complete dedicated heat preparation blocks in their training. Either training in hot locations, or mimicking hot conditions via indoor training and the use of saunas.

Put simply, the more often you train in the heat – the easier it will become. But because heat puts your body under extra strain, it’s important to know how to train and race in the heat safely to avoid putting yourself at risk. It’s also vital that you try to avoid training in the heat in the days leading up to a race – you won’t be able to force adaptations, and you’ll just be putting your body through unnecessary stress that will hinder your performance come race day – rather than help it.

Top tips for training and racing in hot conditions

So that’s the theory. But in practice, what can you do to make training in the heat feel like less of a struggle – and reduce the impact of heat on your race day performance? Here’s our top tips.

Start hydrated

When temperatures soar, it’s important to start thinking about your hydration levels long before you actually set off for your training session or start your race. Hot weather will mean that you’re sweating more and losing more electrolytes than usual, even at rest. This means it’s easy to end up slightly dehydrated, before you’ve even started exercising. Leave it until after you’ve started your session to start hydrating, and you’ll just be firefighting. Putting you at risk of cramps, increased heart rate and reduced performance – which can become dangerous to your health.

Instead, make sure you’re preloading your hydration. Sip on electrolytes an hour or two before you start your training session or race so that your reserves are topped up. Drink to thirst throughout your session/race and use electrolytes to keep your salts balanced.

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Use heart rate data to manage your effort

There’s a strong chance you’ll need to adjust your effort while you acclimatise to hot conditions. Instead of trying to force yourself to hit your usual pace or power output, wear a heart rate monitor and work to your heart rate data. This gives you the best indication of how your body is coping with the heat.

If you notice that your heart rate is significantly higher than usual for the same effort, it’s time to scale things back. This will help you to avoid ‘blowing up’ and risk suffering from heat stress. As your body adapts to the heat, you’ll most likely notice that your heart rate starts to come down so you can hold a higher pace.

In a race scenario, it might feel difficult to slow down and race conservatively. But rest assured – if you overdo it early on, the heat will catch up with you later in the race and you’ll end up slower overall. Pace sensibly, and you’ll be able to stay strong all the way to the finish line.

Use a sports specific sunscreen

We all joke about the silly tri suit tan. But it’s vital to look after your skin when you’re regularly training outdoors in the sun. A regular sunscreen won’t be as effective when you’re sweating and spending extended periods of time outdoors. So be sure to use a sports specific sunscreen such as Pelotan.

Triathlon legend Kristian Blummenfelt says sun protection is crucial for athletes [Photo: Pelotan]

A sports-specific sunscreen will be designed to be water- and sweat-resistant. Essential to ensure you’re protected from UV throughout your training session!

Make sure you apply your sunscreen liberally (research has found that the majority of us don’t actually apply enough to give us adequate protection) and apply it at least 15 minutes before you head outdoors. If you’re racing long distance, it’s also worth having a spare sunscreen in your transition bag so you can top up and avoid having to deal with painful sunburn as well as DOMs the day after your race.

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Time your sessions accordingly

If you’ve got a race coming up which is likely to be a hot one, you might want to make use of any hot weather in the build-up to get some heat preparation done. But resist the temptation to jump right into training hard during the hottest hours of the day. Gradually increase the amount of time you spend training in the heat to give your body time to adapt.

If you haven’t got a race coming up, or if your race is very unlikely to bring hot weather with it, and you don’t need to worry so much about getting heat acclimated. Then it’s worth adjusting the timing of your sessions to coincide with cooler periods of the day. Head out early in the morning, or wait until later in the evening when the sun has started to set.

What to do if it’s hot on race day – PRO tips

We can’t predict the future – or the weather. If it’s unexpectedly hot on race day and you haven’t had chance to get acclimated, try not to panic. There are ways you can manage yourself in the heat to ensure you can still have an enjoyable – and safe – experience.

Adapt your race strategy to account for the conditions

Hot conditions have an impact on your body’s ability to perform. So if it’s hotter than anticipated on race day, you might need to scale back your expected pace/power targets to account for the conditions.

As we’ve outlined earlier on, your heart rate is a really valuable metric here to get some real time feedback on how your body is coping with the conditions. If it’s significantly elevated, be prepared to reduce your effort to keep it in a sustainable zone. It can be tempting to push through and hope for the best – but more often than not, you’ll end up hitting the wall later in the race. Which can not only be race ruining – it could also put your health at risk.

Maximise the aid stations and don’t forget to fuel – Lucy Charles-Barclay’s PRO tips

Ahead of the T100 race in Singapore earlier this year, we caught up with IRONMAN World Champion Lucy Charles-Barclay (who beat the Kona heat to take the crown in 2023) to get her top tips for age-groupers who were taking on the amateur 100km event in the notoriously hot and humid conditions that Singapore always delivers.

Lucy recommended making the most of the cooling available out on the course – using water, ice and sponges from the aid stations to cool yourself down. A great tip she shared was to also hold the ice from the aid stations in your hands to maximise the cooling effect. “Use ice as much as possible, keep it in your hands and keep it in your mouth – hopefully that will keep you a bit cooler!”

Another important tip from Lucy Charles-Barclay for racing in hot conditions is to not only make sure you’re drinking enough, but to ensure you’re fuelling too.

“Make sure you get the carbs in as well, that was something I struggled with last year. Because it’s hot, you’re thinking all about getting the water on board. But make sure you’re getting that energy on board as well.”

Lucy Charles-Barclay speaking to TRI247 ahead of Singapore T100

Know the signs of heat stress

Whether it’s a training day or race day – it’s important to know when ‘a bit hot’ has crossed over into ‘too hot’. Heat stress (or heat stroke) can get serious pretty quickly so make sure you know the signs. If you start experiencing symptoms such as headaches, nausea, dizziness, a rapid pulse (beyond what would be normal for the effort) or faintness. It’s time to stop and get help. Nothing is worth compromising your health!

Keep an eye on your training buddies and fellow competitors too – if something doesn’t look right, get them into the shade, cool their skin with water or a fan (avoid ice water as this could cause shock) and get them to sip on electrolytes. If in doubt, get medical help.

Looking for more training tips and advice? Head to our triathlon training section for more!

Jenny Lucas-Hill
Written by
Jenny Lucas-Hill
Jenny Lucas-Hill is a writer, content creator and communications professional. A long-distance triathlon enthusiast, she has four full Iron-distance finishes to date & also loves watching the sport.
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