The Bikram backlash

Madonna and Gwyneth Paltrow are flexible fans. But evidence is mounting that this radical form of yoga could be a stretch too far

Conducted in sweltering temperatures of 43C, there's no doubt about it: Bikram is the hottest form of yoga around. Barely heard of in Britain just two years ago, Bikram now has centres around the country, flocked to by fashionable devotees. The reason for its popularity is clear. Stretching in high temperatures, say fans, means you can push your body twice as far - which means you really see results. And, as for all the sweating, it's a wonderful way to detox.

Conducted in sweltering temperatures of 43C, there's no doubt about it: Bikram is the hottest form of yoga around. Barely heard of in Britain just two years ago, Bikram now has centres around the country, flocked to by fashionable devotees. The reason for its popularity is clear. Stretching in high temperatures, say fans, means you can push your body twice as far - which means you really see results. And, as for all the sweating, it's a wonderful way to detox.

But Bikram is facing a backlash. Growing numbers of physiotherapists and yoga teachers are warning it may be a stretch too far. Low-back pain, injuries to hamstring muscles, knee sprains and damaged cartilages are some of the Bikram-related injuries that have been reported by physiotherapists in London and America.

Dr Robert Gotlin, director of orthopaedic and sports rehabilitation at the Beth Israel Medical Centre in New York, says he sees up to five Bikram-related injuries a week. The problem, he says, is that if you stretch any muscle too far beyond its resting length, it will cause damage.

Other injuries relate to moving from extreme heat to cold without giving the body an adequate "warming down". "In the heat, you are lulled into a false sense of security," says Sammy Margo, spokeswoman for the UK's Chartered Society of Physiotherapists. "You can stretch muscles beyond their natural limit, and in the process you can tear or strain them. Another problem is after the class. When you walk into a cold changing-room, your heated muscles can suddenly contract, causing them to spasm."

In each Bikram yoga class, 26 hatha poses and two breathing exercises are performed in a specific order. Each posture is repeated twice, with the aim of pushing the body a little further each time. However, several postures significantly stress the knees, increasing the risk of tearing cartilage, a shock-absorber for the joints and legs. According to Dr Gotlin, these include the toe-stand pose, consisting of a single-legged squat, and the fixed-firm pose, which involves sitting backwards with bent knees. The hip joints may also be prone to over-rotation in some Bikram moves. This can overstretch the ligaments, leading over time to loose joints.

Margo regularly sees people with Bikram-related injuries. "Most commonly, we treat people for knee and low-back problems," she says. "We also come across quite a few neck and shoulder strains."

As a yoga style, Bikram remains more popular than ever. Its founder, Bikram Choudhury, developed it after he suffered a severe knee injury from weight-training. Using heat to assist mobility and encourage healing, he developed the technique as part of his own rehabilitation. Choudhury subsequently set up a company - The Bikram Yoga College of India - in Los Angeles in the 1960s to spread his copyrighted method.

Today, his company has more than 350 affiliated studios worldwide. Five centres in London and three centres elsewhere in the UK have opened since Bikram came to Britain seven years ago. As yet, though, no Bikram centre is recognised by the British Wheel of Yoga, the national governing body of the ancient art form. With most other yoga forms, teachers must be qualified and adhere to the British Wheel's strict standards of practice.

Jane Kersel, an Iyengar yoga teacher at London's Triyoga Centre, turned down the opportunity to teach a similar form of "hot yoga" several years ago. "I worried that using heat to enhance stretching would attract people looking for fast, visible results," she says. "But these are the very people who might push it too far, and injure themselves. The yoga philosophy is about connecting with your breath and finding your own way - not pushing yourself."

She also worries about exposure to intense heat. "While other forms of yoga allow the body to heat internally, at a natural rate, the hot rooms at Bikram centres heat the body at an unnatural pace. This can cause a build-up of lactic acid in the muscles, which can lead to rebound stiffness the next day."

Nick Morgan, an exercise physiologist at Lilleshall Human Performance Centre in Shropshire, says sudden temperature changes after a class can put the body into shock. "A sudden drop in temperature can make blood vessels and muscles suddenly contract," says Nick, who advises stretching in a cooler room for 10 minutes after a session. "And your immunity is likely to drop, leaving you prone to illness."

Good hydration could also be a problem. "At these temperatures you lose a lot of fluid, even without any physical activity," says Morgan. "Dehydration, whether mild or moderate, weakens a range of physical and mental functions. To keep hydrated in these classes, you'd probably need to drink at least a litre of water during the session."

And he isn't convinced the heat means you'll get flexible faster. "In the short term, stretching in a hot room is unlikely to make a significant difference to your overall mobility. You could get the same results by doing 20-30 minutes of stretching at room temperature three times a week."

None the less, Bikram yoga has a strong following of people who have experienced benefits from it. "I'm convinced Bikram yoga helped me heal after I broke a bone in my left foot last year - each class would leave me feeling more mobile," says Lizzie Smythe, 36, a London-based events organiser. "After three weeks, I was walking without crutches. It's also helped me recover from a knee problem."

And advocates claim - regardless of your level of fitness and flexibility - that the method is safe and beneficial. "Bikram is designed to reduce your injury risk, not cause injuries," argues Armand Mertikian, a Bikram yoga teacher in Chiswick, west London. "Most injuries stem from not warming up properly - stretching in a cold church hall when you are stiff is the worst thing you can do. The heat of Bikram classes prevents just that.

"The technique's safety is compounded by the fact that all Bikram teachers have to undergo a thorough training," he adds. "I've been teaching this form of yoga for five years and I have yet to witness an injury."

Even though the backlash against Bikram has started, there are three new forms of yoga that are set to become the next big thing for devotees.

Rope yoga involves working through a series of yoga moves while attached to ropes on a pulley, which supposedly deepens your body's stretch. The method focuses on strengthening the abdomen and thighs.

Jivamukti yoga has already taken off in New York, where Donna Karan, Christy Turlington and Sting attend classes, and a centre is due to open in London. It combines physical yoga with chanting, music, meditation, ancient mystic philosophy and devotional practice.

Yoga raving was also developed in New York, and is coming to the UK later this year. Using basic yoga techniques with guided dance moves, the aim is to open up the "raw wave" energy in your spine.