Turns out hot yoga may do your health more harm than good.

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Combining a supposedly relaxing exercise with the intense atmosphere of a sauna may not be everyone’s idea of a good time, but Bikram yoga has proved a fast favourite amongst yogis.

It claims to improve mindfulness, flexibility, strength, muscle tone and general fitness. It’s hot. It’s hard. It’s very, very sweaty. But then again, if you don’t leave the class covered head to toe in your own (and others) perspiration, does it really count as exercise?

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A new study has revealed that practicing yoga in a hot room can raise internal body temperatures and heart rates to levels that may be dangerous for some.

“The dramatic increases in heart rate and core temperature are alarming when you consider that there is very little movement, and therefore little cardiovascular training, going on during class,” says study author Emily Quandt. (Post continues after gallery.)

A Bikram class is typically 90 minutes long and is confined to a room that is around 40 degrees Celsius and 40 per cent humidity.

The study, sponsored by the American Council on Exercise and published in the Gundersen Medical Journal, looked at 20 regular Bikram participants, seven males and 13 females, between the ages of 28 and 67 years-old. Each participant swallowed a core body temperature sensor and was given a heart rate monitor to wear during the class

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The results showed that many of the volunteers’ core temperatures reached higher than 39 degrees celsius, with one man’s temperature reaching higher than 40 degrees celsius. A body temperature of 37 degrees celsius is considered normal.

Although none of the volunteers exhibited any signs of heat intolerance, researchers pointed out that it is common for heat illness and heat stroke to happen when internal temperatures reach these levels.

“Although there are potential benefits associated with practicing Bikram yoga, the potential for heat intolerance among some students, including those who may not yet be acclimatised to the heat, should not be entirely overlooked,” say the study authors.

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Researchers also found that the average heart rate was 80 per cent of the predicted maximum heart rate for men and 72 per cent of the predicted maximum for women, with the highest heart rate for women in the class at 85 per cent of the predicted maximum and 92 per cent for men.

While the research is definitely something to keep in mind, it doesn’t mean you have to give up your weekly dose of Birkam. To minimise the risks, the researchers suggest lessening the duration of your class and lowering the temperature.

The best thing you can do to survive the heat? Stay hydrated.

"Exercising in hot and humid environments - whether inside a studio while practicing Bikram yoga or outside running during the warm months of summer - can place participants at risk for heat-related illness, especially if those individuals do not adequately hydrate before, during and after exercise," say the study authors.

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If you're already a Bikram yoga devotee: great. However if it's something you were thinking of starting, be sure to take into account or check with your doctor about any health concerns - and maybe warm up (literally) with a few sauna sessions first.

Do you do Bikram yoga? Have you ever had any health problems because of it?