NEW YORK When it comes to yoga, some like it hot but not too hot.

So yoga studios and fitness centres are finessing the tenets of hot yoga as set forth by the master, to find the middle way.

“Some people are turned off by the heat, some people are addicted straight off the bat,” said Brooke Eddey, a hot yoga instructor at Crunch, the national chain of fitness centres.

“Our room is around 90 degrees. If it gets too hot, I turn it off.”

Such thermal flexibility would be anathema to the strict followers of hot yoga guru Bikram Choudhury, who keeps a firm grip on both thermostat and sequence at his nearly 500 studios franchised worldwide.

A Bikram yoga room is heated to a steamy 105 degrees Fahrenheit, with a humidity of 40 per cent. Even the founder calls them torture chambers.

“The heat helps you to stretch safely and has its own detoxifying benefits,” explained Ainslie Faust, spokesperson for Bikram's Yoga College of India, in Los Angeles, California.

Faust said Bikram's series of 26 postures were selected because they are the most healing poses for the common problems of people living in the Western world.

“We modify it,” Eddey said simply. “I've taken a lot of Bikram and I think the 26 poses are a great system, really well thought out. I get that, but I also incorporate some flow, some vinyasa.”

Vinyasa is yoga-speak for breath-synchronised movement. It's another departure from the Bikram style, which is to hold each posture for a minute or so before proceeding to the next.

“I love the movement,” said Eddey. “It lets the whole body open up. And we stay hydrated consistently,” she said, “whereas some Bikram classes want you to stay with the 'present'.”

Fabio Comana, an exercise physiologist with the American Council on Exercise (ACE), believes exercising in extreme heat can be dangerous, vinyasa or no vinyasa.

“You may think it's purifying and cleansing but you have to respect the physiology of the body,” he said.

“The human body is designed to tolerate temperatures between 97 and 100 degrees. It's not designed to go outside those numbers,” he said. “Core temperature can go up very quickly. Over 105 degrees you will start to damage protein.

It's cause and effect.”

He added that after a Bikram workout, if any weight is lost it's not a good thing because it is fluid that has been lost.

Tanya Boulton, managing teacher at Pure Yoga in New York City, says temperatures in Pure's hot yoga studio can approach 100 degrees, so it's wise to build tolerance slowly, while taking plenty of breaks.

“You have to really prep yourself for hot yoga. You have to stay on top of hydration and be aware that you're sweating a lot more than you normally do,” said Boulton.

“We teach hot power yoga, which is about an hour long with a lot of movement,” she said, “And hot Ki yoga, which combines martial arts with vinyasa flow and rock music.”

Boulton said everything taking place in your life is reflected on the mat.

“Sometimes the heat bothers you, sometimes it doesn't.”—Reuters