The physical improvement in Andy Murray over the past 12 months has been well-documented and was plain for everyone to see last weekend when the British No 1 kicked off the 2008 season in style by winning the Qatar MobilExxon Open for the fourth ATP title of his career.

But the Scot, who lost at the AAMI Classic eight-man exhibition event in the Melbourne suburb of Kooyong this morning as he completes his Australian Open preparations, revealed yesterday that there is a secret ingredient in his new fitness plan: yoga.

Not just any old yoga, though. Bikram yoga. Described as the fastest-growing yoga in the world, it takes place in a room heated to 42C (107F) and is designed to increase flexibility and strength, as well as helping to prevent and heal injuries.

Murray got involved with Bikram yoga through Jez Green and Matt Little, his fitness consultants and two members of the support group he hired after his split from Brad Gilbert, his former coach, in November.

Looking lean and strong as he trained yesterday at Melbourne Park, the venue for the Australian Open, which begins on Monday, Murray said that the yoga was already making a big difference.

“Until you do it, you can’t comment on how difficult it is,” Murray said yesterday, demonstrating one of the exercises as he spoke. “I did some tough fitness work in the off-season, but that’s one of the hardest things to do.

“It’s because it’s done at 42 degrees. Regular yoga just looks like normal stretching to me. It’s not as much fun, whereas this, with no windows and with 20 to 25 other people in there just trying to hold postures and stay balanced and concentrated the whole time, it’s really tough.

“I can’t really do any of the good stuff yet but if I keep doing it, then in about six months, I think there’ll be a huge improvement in flexibility and strength. It’s all about progression and going a bit further each time. It’s perfect because you can actually tell if you’re improving because you can either do the exercise or you can’t.”

Murray has been lifting weights and working hard in and out of the gym for a long time, but he said the new element to his fitness regime was just as significant. “It’s just something that I think is really important,” he said.

“Being tennis players, we get very stiff, especially changing surfaces a lot. In the off-season, when you’re doing a lot of training, it’s a great way of getting used to the heat and also improving your flexibility. When you are just stretching after matches, you are just maintaining your flexibility, but this improves it a lot. Matt used to do it with a lot of players at the NTC [National Tennis Centre, in Roehampton, southwest London]. I’ve done five or six classes now and it’s been really good fun.”

Murray, whose win in Doha lifted him to No 9 in the world, is joined by four other members of the top ten in Kooyong. Although Roger Federer, the world No 1, withdrew because of a stomach virus, Nikolay Davydenko, of Russia, Andy Roddick, of the United States, Fernando González, the Chilean, and David Nalbandian, of Argentina, are present for an event that gives players the chance to get used to the new Australian Open surface, Plexicushion, while offering them a minimum of three matches.

Murray was due to begin his campaign against Marat Safin, the former world No 1 from Russia, in the early hours of today. Marcos Baghdatis, of Cyprus, who replaced Federer in the draw, and Ivan Ljubicic, of Croatia, complete the lineup.

Taking a flexible approach:

- Bikram yoga was created by Bikram Choudhury, who was born in Calcutta but now lives in California. It is derived from the 5,000-year-old Indian practice of yoga, at which Choudhury, 61, was Indian champion four times, but conducted in temperatures of 42C (107F) and at a humidity of 50 per cent - ostensibly to emulate conditions in India - which helps participants to loosen their muscles and sweat out toxins.
- Famous fans of Bikram yoga, apart from Andy Murray, include Elle Macpherson, George Clooney, Daniel Craig and Peter Mandelson.
- In 1973, Choudhury set up his first yoga studio in Los Angeles. More than 30 years later, The Wall Street Journal valued the yoga industry as being worth $42 billion (about £22 billion) worldwide.
- Bikram yoga features 26 postures and two breathing exercises, performed in order. In 1978, Choudhury claimed copyright to his programme and had it trademarked in 2002, to the annoyance of many who felt it was akin to taking out property rights on verses in the Bible.
- Choudhury is said to be worth $7 million but that is increasing rapidly. He has developed a Bikram yoga brand: people can buy official clothing, jewellery, DVDs and CD recordings of Choudhury singing his own compositions.
- There are hundreds of affiliated studios worldwide. To keep pace with his expansion plans, the training course for new Bikram teachers, which originally took four years, now lasts a couple of months. Choudhury has written a script for lessons, which teachers have to learn.
- However, there have been warnings from physiotherapists that Bikram yoga causes lower-back pain, injuries to hamstrings, knee sprains and damaged cartilages.

Words by Patrick Kidd.