Is hot exercise a smart idea?
A hot yoga session in a heated room is nothing new but how about 60 minutes of cardio in a room heated to 32 degrees with humidifiers thrown in for added steam?
Sounds like a torture chamber but it’s the latest workout from US celebrity trainer Tracy Anderson – a Zumba-ish cardio class called Tava which, reports the Los Angeles Times, incorporates heat to “loosen muscles and improve skin tone and elasticity”.
Anderson’s methods don’t always stick to exercise science. She’s the one whose weight training approach maintains women should lift nothing heavier than a 1.3 kilo dumbbell in case (shudder) they bulk up.
So is there evidence to back this hot cardio approach – or can too much heat ruin a good workout?
“High temperatures, especially with high humidity, make it difficult to perform to anywhere near your full potential – it turns what should be a quality training session into something much harder,” says Ray Kelly, an Accredited Exercise Physiologist and spokesperson for Exercise and Sports Science Australia.
That’s partly because your body’s cooling system needs blood to help redirect heat from your core to the skin – and this can reduce the extra blood supply that heart and muscles need during exercise, he explains.
Humidity also makes it difficult for sweat to evaporate – and that makes it hard for you to cool down, he explains.
“While sweat allows heat to escape your body it’s the evaporation that has a cooling effect – not the sweat itself. But sweat doesn’t evaporate as easily in humid air, he says.
“The only time training in the heat is useful is if you have to acclimatise for sports performance in hot conditions.”
While hot yoga in a room heated to 40 degrees might be less arduous than jumping around in a hot cardio session, it can still be problematic for anyone with underlying problems with blood pressure or heart disease – both heat and dehydration can increase blood pressure, Kelly says.
But is there a case for using warmer temperatures to promote flexibility? Some studios now offer yoga and Pilates classes in rooms warmed to 27 degrees, for instance.
“There’s a lot of conjecture around whether heat can improve flexibility or ‘detoxify’ the body which are some of the benefits that hot exercise programs claim but there’s very little in the way of sound science to support these claims,” says Alisha Smith, Learning and Development Manager with the Australian Fitness Network, the organisation which trains fitness professionals.
Like Ray Kelly, Smith says that rather than improving a workout too much heat can compromise performance – which typically means fewer results for your effort.
“However there’s some emerging evidence that training in hot conditions forces your body to get better at temperature control – but it needs more research to flesh this out,” she adds.
Is there an ideal temperature for an indoor workout? The American College of Sports Medicine (ACSM) recommends a comfortable 20 to 22 degrees but Australia has no similar guideline for its gyms and fitness centres, according to Fitness Australia, the health and fitness industry association.
“Part of the challenge of recommendations around training in the heat is that everyone’s tolerance to temperature is different which means that picking a number would be arbitrary,” says Alisha Smith. “If I put my untrained cool weather loving grandmother and a fit young runner from the tropics side by side on a treadmill in a hot gym with low air flow and no fans, both will have vastly different experiences.“
The fitter you are, the more efficient your body is at regulating your temperature, according to the ACSM – you’ll start sweating earlier and you’ll cool down faster.
Good hydration also makes a difference – going into a workout dehydrated means your body won’t sweat as efficiently as it should, causing an increase in body temperature – the ACSM’s detailed hydration guide recommends drinking around 470 to 600 mls of water at least four hours before exercise and 250 to 350 mls ten to 15 minutes before you start.
And just for the record, you can’t sweat yourself slim says Ray Kelly who’s known some people to wear plastic wrap under their gym clothes in order to sweat more and lose weight. Any weight lost is only from fluid loss and will bounce back once you rehydrate.
On the other hand, there are a number of health benefits associated with working out in cold temperatures.
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