As summer kicks into full force here in the UK, I see more and more comments about how heat is affecting training – both from others and myself! Running in the heat is hard, as is doing any form of exercise that raises your temperature. Our bodies work hard to maintain a stable internal environment and when that’s put under pressure, it has to work even harder to keep everything steady. If you learned about homeostasis at school you’ll know all about this!

The ideal temperature for endurance running is 9.5 – 11 degrees C (50F, with women preferring the upper end of this). For sprints, however, the optimum temperature is around 22 degrees C (72F), showing that the best temperature for training depends on what you’re doing, as well as personal preference. However, there are numerous benefits to training in the heat, not to mention it’s fun to get out on a sunny day! So long as certain precautions are taken, there’s no reason hot days shouldn’t be enjoyed just like any other.

What happens to your body when you train in the heat?

To compensate for the warming temperates created from exercise, your body sends more blood to the skin, allow heat to be lost via convection, radiation and evaporation. The warmer and more humid the external environment, the harder it is for heat to dissipate quickly, meaning you’ll cool down more slowly.

There are many physiological changes that occur to keep you cool, but after a point they may not be able to keep up. If your body gets too hot, it starts to rebel, telling you to slow down, drink, maybe even have a sit down. The first symptoms of heat exhaustion are dizziness, nausea, headache, extreme fatigue, cramps and mild confusion. Pushing through exhaustion can lead eventually to heat stroke, with the result being damage to vital organs as the body’s internal thermostat goes out of whack. It’s advisable to slow down long before this point, and planning your nutrition and hydration can stave off heat exhaustion for a long time.

How to train in the heat

It takes our bodies one to two weeks to adapt to training in the heat, which is why training can be especially hard at the start of summer – as soon as you get used to running at one temperature, it gets hotter again! In addition, beginner runners and people new to exercise will be less optimised to cool down quickly – the more you exercise, the more efficiently your body learns to cool. Hence very fit people may sweat more, and less fit people may need to take it easier on hot days! There are, however, certain things you can do to still make the most of hot days, and make sure you’re keeping safe when you train.

• Avoid training in the hottest part of the day. Aim for early morning for the best temperatures (there’s also nothing nicer than a run at the start of a glorious summer’s day!).
• Replace lost electrolytes (salts) with dietary salt or an electrolyte drink/rehydration salts.
• Make sure you are hydrated well before heading out on a run or to the gym. This doesn’t necessarily mean glugging 2L of water before heading out, but make sure you’re hydrated the night before and morning of a big run or training session. If you’re working out for a long time, take water with you.
• Wear sunglasses, a cap and light clothing to reduce the effect of the sun when outside. Always wear sweat-proof suncream.
• Take it easy. As you acclimatise, your training sessions will get easier, but while you’re adapting, train by effort, not data. This means you may be running slower, shorter and lifting lighter with fewer reps, but that’s ok! The effort you expend is the same, and it’ll leave you a better athlete.
• Avoid training on the hottest days if you’re concerned. It is possible to plan training days around the weather – I often do this to avoid rainy or extremely hot days, and train either side of those days.

The more you train in the heat, the more tolerant you will be to it. Stick it out, knowing that your runs/workouts may be compromised in the meantime, and within a week or two you’ll be amazed how normal it feels. Think of it as training adaptation – in the same way that training stresses out the body to make it more adapted, heat does the same. So long as you’re being sensible with hydration and your goals, there’s no reason not to train on hotter days. It’s just up to personal preference!

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