Another week, another heatwave – but bracing for a sweaty workout doesn’t mean your whole fitness routine has to suffer. If you’re wanting to keep business as usual, Dr Tom Brownlee, Elite Performance Expert and member of the Performance Advisory Board at Myprotein, shares how to exercise safely in a heatwave
Words: Amy Dowrick | Images: Shutterstock
As the Met Office issues more extreme heat weather warnings and we see temperatures exceed 86°, it’s going to start feeling harder to carry on with life as normal – but sticking to your schedule might be just what you need to avoid succumbing to those sweaty nights for good.
What happens when you exercise in a heatwave?
If it feels like harder work, that’s because it is – but the strain you feel is mostly cardiovascular and central rather than in the muscle itself.
“Blood is diverted to the skin to dump heat, leaving less for working muscle, and you burn through stored carbohydrate faster,” says Dr Tom, an Associate Professor in Applied Sport Sciences at the University of Birmingham.
“A lot of what feels like tired legs in the heat is actually your brain pulling back to protect your core temperature,” he adds. “Also, as we sweat our blood becomes thicker as the body loses fluid, which means our heart has to work harder to move the relatively thicker blood.”
How to manage your routine during a heatwave
Dr Tom suggests it’s mostly about managing expectations – and adapting your routine accordingly.
“You can train, but don’t expect the same numbers,” he says. “Heat gives your body a second job, cooling itself, so drop intensity or volume by 10 to 20 % and judge effort by feel rather than the clock or the load.”
“It is a compromise as performance drops,” he adds. “But repeated exposure drives real adaptations.”
According to Dr Tom, as you maintain your routine and keep up exercising during the first one to two weeks of a heatwave, your blood plasma volume expands, making you sweat earlier and more efficiently, and your heart rate at a given effort falls.
“Those changes carry over and can benefit you even in cool conditions, which is why some endurance athletes deliberately train in the heat before big events,” he adds.
Dose up on electrolytes
Sometimes, drinking water just isn’t enough – and there’s an expert trick that a lot of people ignore.
“Some fixate on water and protein, but in a hot, sweaty session it is the salt you lose that matters most, and sweat sodium varies enormously between people,” says Dr Tom, who says that some of us may lose two or three times more than others.
“If you are cramping, getting headaches or feeling flat despite drinking plenty, you are probably under-replacing sodium rather than water,” he adds. “For a normal hour-long session, water is fine – but once you are sweating heavily for longer, add electrolytes.”
Consider the time of day
In a heatwave, timing matters more than people think.
“Early morning is usually the coolest part of the day and the safest window,” says Dr Tom. “Your body is primed for marginally better performance in the early evening, but in summer that is also when accumulated heat is highest, so the environment outweighs the small physiological edge – so train early if you can.”
Take an ice bath
“After genuinely hot exercise, cold water immersion does more than feel good; it physically pulls your core temperature back down, and people report feeling fresher,” he adds. “The caveat is timing relative to your goals: routinely jumping in the cold straight after resistance training can blunt the muscle and strength gains you are working for.”
If you’re wanting to include ice baths in your routine, use them for cooling and recovery after hard or hot sessions – not as a default after every gym workout if building muscle is your aim.
How to know when to stop
But it’s also important to not get too carried away with working out in the heat. While excess sweat might feel like a sauna trick, you must keep an eye out for the warning signs, such as light-headedness, nausea, an over-elevated heart rate, or suddenly going cold and clammy.
“Those mean your core temperature is climbing faster than you can shed it, and pushing on from there is where heat illness starts,” says Dr Tom.
Dr Tom Brownlee has over 15 years’ experience working across elite sport as a practitioner, researcher and consultant. His work spans strength and conditioning, physiology and athlete development, and he has collaborated with organisations including the Premier League, Formula 1 and the NFL. For more information about what he does visit myprotein.com/thomas-brownlee
