There are classes in Santiago, Chile; Beijing, China; all across America and now, finally, Clarkston. At last Scots have the chance to try out the only fashionable way to get sweaty: Bikram, or “hot” yoga. Ever since the homegrown tennis star Andy Murray credited the extreme workout with helping him to beat the world number one, Roger Federer, the phone of the Bikram teacher Lisa Miller has been as hot as the LA studio of the method's guru, Bikram Choudhury.

Murray's trainers suggested he try the classes, which last a gruelling 90 minutes in a room heated to 40C, in preparation for the Australian Open. To his delight, he found that it improved not only his fitness, flexibility and ability to cope with high temperatures, but also his “mental strength”. “I've been mentally weak for such a long time and not held up in pressure situations,” he said after the match with Federer in Dubai.

“I think I showed that was not going to be an issue. The most important thing is to believe you can win the match. It's important to stay patient and not make rash decisions early in the match. I didn't do that - I stayed calm the whole way through.”

For its devotees - and there are many, this is a highly addictive form of exercise - Bikram yoga is a workout for the mind, body and spirit that is hard to match. Banish images of the community centre where ladies in jogging bottoms lie on a tartan rag and creak into the lotus position. Every class follows the same punishing format, as designed by Choudhury, the former Indian yoga champion turned entrepreneur. There is a set programme of 26 poses and two breathing exercises, performed twice: balance poses, warrior poses, front bends and back bends. Perspiration is not optional.

Murray is not the only famous face to pop up in shorts and T-shirt, ready to put his head on his knee and keep smiling. Madonna, George Clooney, Elle Macpherson, Goldie Hawn, Barbra Streisand, Raquel Welch and Julia Roberts are just some of the enviable bodies who have found that a cobra pose in a steam room creates the long, lean muscles and taut, toned body that the red carpet demands.

Not that Lisa Miller is expecting a wall of paparazzi stopping the traffic at Clarkston Toll. Her classes will be starting off small and exclusive, with just six people in a little room above a beauty salon. The initial plan to hold three a week has already been revised upwards and she is adding a Sunday morning session to the week-night timetable. For the future there are further ambitions: a dedicated studio with daily classes and, she hopes, another Scottish teacher.

Miller, 27, is a walking, hair-tossing advertisement for Bikram, with peachy skin and an enviably lean, pert body. And although the Glaswegian was fit before she discovered hot yoga - she was working as a personal trainer when a friend took her to her first class - she is convinced that this offers something more.

“It's not just running on a treadmill that keeps you fit,” she says. “There's all the other components: flexibility, breathing. I developed strength with my breathing that I could use when I did running and other things. When I did my first Bikram class I felt as if I wasn't actually that fit. I said to myself, hold on, this is something different.

“When you get to the end of the class and you've been through all that and you haven't walked out, your body's alive and zinging. Your body's saying, thank you, you can feel it.

“In an aerobics class you're working your physical body. You can be working really hard but thinking about something else. With Bikram, you walk out and know something else is working, your soul's working, your mind, body and spirit connection. As Andy Murray has discovered, it builds determination, it builds patience. When you walk out the door you're ready to take on the world because you have been through what can feel like the hardest 90 minutes of your life.”

But it was far from love at first back bend. “I actually left halfway through the class. I stood outside and thought, what is that all about? They're crazy. They're off their heads. I had to just give myself 10 minutes or so, then I went back in.” She finished the class, but it was not easy. “I had to let go of my ego in there. I was a beginner, in this hot class. I was sweating ...”

However, Miller persevered and by the end of 90 minutes she was hooked. “I thought it was great, I slept better, I started to stand better, I felt I could take on more, I was more assertive, I felt better about myself.”

Aged just 23, Miller saved up her $5,000 (£2,500) fee and decamped to Los Angeles to train as a Bikram teacher with Choudhury himself. “That was,” she recalls, “really extreme. There were 300 people in a huge room, an inch between each yoga mat. I think I had two or three nervous breakdowns just dealing with everything that went on there.”

Then, after teaching in Australia for two years, Miller did the thing she thought she would never do: she moved back to cold, grey, Bikram-free Scotland.

“I had no plans to stay because there was no Bikram here,” she says. “But things change. I met my partner and started teaching.” But old-style hatha yoga in a cool room was just not the same and Miller was desperate to find a way to bring hot yoga to her homeland. This was partly for entrepreneurial reasons: “I felt I had this great product and wanted to do something with it”, and partly for selfish ones. She has to do her own practice every day and, with no 40C studio in Scotland, Miller had to buy extra heaters to transform her bedroom in Cumbernauld into the next best thing.

Starting a Bikram class is not as simple as hiring the church hall and handing out leaflets at the mother-and-toddlers group. Draughts are the enemy: the room needs to stay hot and humid for the duration of the class. It should have mirrored walls. There must, obviously, be showers and changing facilities. After failing to interest health clubs and gyms, Miller decided to contact smaller spas and beauty salons, and when she met Janice Clyne, the owner of Sano Spa in Clarkston, she knew she had found the place. The room is small - it will certainly be a cosy class - and contains the spa's infra-red sauna.

Having found the right premises, all Miller needed were the right pupils. And that is where Murray comes in. “He has brought so much awareness to people,” she says. “Ninety per cent of my calls have been from men. One was a policeman for 30 years and he's now doing personal training, another is 55. They are from all different walks of life.”

And if Murray should fancy a session when he is visiting his family, Miller would be delighted to help out.

For details of Lisa Miller's classes call 07853 001 332