Standing with six other women in a room lit only by candles, with my feet bare and arms loosely hanging down, I begin twisting my torso from side to side, letting my arms swing out with each turn. I feel like I'm six again, pretending to be a wind-blown tree. "Now, you should focus your awareness on the movement in each and every vertebra," says our teacher, Simon Low, who gives precise instructions in a soothing voice. The muscular loosening in my lower back is so pleasant that I even stop fretting that my toenails aren't as perfectly painted as the woman standing next to me.
I am a yoga rookie, so for most of this two-hour class I'm only able to (rather inaccurately) mimic Low's elegant postures. But even I can tell that there's something about the flowing sequence of movements through which he leads us that is slightly different from mainstream yoga. This is "Yin & Yang" yoga – the latest rereading of the ancient Indian system of personal development that aims to balance body, mind and spirit.
Since the 1990s, when stars such as Geri Halliwell and Madonna credited their iron-hard abs to daily yoga practise, yoga has become the favoured exercise regime of those striving for thinness. But besides weight loss, toning and stress relief, its physiological benefits are also well-documented. Clinical studies in the last decade have shown that yoga helps to reduce the frequency of asthma attacks, is beneficial to those with rheumatoid arthritis and can treat both carpal tunnel syndrome and hyperventilation. Its religious foundation often ignored by students in the West, yoga today is mainstream: you're as likely to see a class on the timetable at your local gym as you are an aerobics or spinning session.
But for most people, it's not enough to say they simply practice yoga. Even the casual student will emphasise a loyalty to a specific style: Hatha, Ashtanga, Bikram, Iyengar. This year, expect to see Yin & Yang join the ever-growing list of hybrids. It has arrived in the UK largely thanks to Low, a co-founder of Triyoga, the Primrose Hill centre that counts Sadie Frost and Kate Moss among its regulars.
Low emphasises that Yin & Yang not a system he has invented or intends to copyright. "I don't really want to portray it as something new, because the elements on which it is based have always been there," he tells me after our class. As with any style of yoga, it combines physical postures (asanas) with controlled breathing (pranayama). But in several ways it is unique: the program combines a balanced number of passive asanas inspired by Chinese Taoist yoga (the Yin part) and an energetic, flowing sequence that will challenge the most experienced students (the Yang part).
"A Hatha or Ashtanga yoga student would recognise most of the postures from the Yang section," says Low. "But there are spiralling aspects to the movement that perhaps traditional yoga practitioners will be a little less familiar with. But once they do it, they'll find the body responds very favourably."
The Sun Salutations in the Yang section I certainly remember from the handful of Ashtanga yoga classes I've struggled through (including the dreaded Chaduranga Dandusana, essentially an agonisingly slow push-up). But to such classic postures Low has added spiralling hand and arm movements that evoke Tai Chi. "I'm still strict about the position of feet, pelvis and neck, but in between those key points, which are the classic areas of yoga injury, you can let go." He believes that these circular, expressive gestures not only help to work on stiffened joints but allow a freedom of interpretation that he says many in the yoga community feel is missing from highly regimented classes. "It's a softer kind of yoga," he says.
The Yin section involves lying on the thin foam mat, spending four or five minutes in various postures designed to open up the hip joints, the pelvis and "allow the spine to breathe," says Low. Carefully controlled breathing allows the stretches to deepen into what would otherwise be painful positions. The energy channels discussed in Chinese medicine also informs the Yin postures, he explains. Students are asked to become aware of the movement within a still body, and as I gradually stop fidgeting on the bolster that supports my back, I can sense what he means: your slow breathing, your heartbeat and pulse become hypnotic. It's very relaxing.
Low, who is originally from Sussex but who first learned yoga in the US, has been teaching and practising for 15 years, but says the perfection of his Yin & Yang method is the summation of his life's work. He doesn't claim to have invented it – in fact he gives credit to other teachers for "guiding" him in its finer points, most notably the American yogis Sarah Powers and Paul Grilley. But in the UK he has trained six cohorts of teachers in it, and has just released a DVD that includes detailed demonstrations.
Inevitably, my experience back at home with the DVD is more challenging: I can't see the television when I'm prone in the Yin positions, and the Yang section is so fast-moving I begin to think it might be less stressful to go out for a jog in the inner-city traffic. The instructions are precise and easy to follow, but it's no substitute for a taught class – most would need a beginner's course to get started, and from there move on to "self-practice".
Low now does most of his teaching at weekend retreats in the British countryside or in Thailand and Spain, and classes tend to be booked well in advance. But he thinks Yin & Yang has been so popular with yoga teachers that it is only a matter of time before it appears on the timetables of your community centre.
"Explore local classes, it's easy to find them now," he advises. "In fact, the British population has never been so well served by yoga practice. It's a life-changing and life-affirming experience. In the beginning, people tend to say, 'I'm not flexible enough for yoga' or 'I've got dodgy knees'. They just think of the physical postures. But the truth is, if you can breathe, you can practise yoga."
'Yin & Yang Yoga with Simon Low' is now on DVD by Acacia; www.simonlow.co.uk
The health benefits
* Shri K Pattabhi Jois, the foremost exponent of Ashtanga yoga, says that yoga "balances the mental, physical and spiritual pressures and stresses posed by the modern world".
>* Often, the first part of a yoga class is dedicated to deep, rhythmic breathing, which practitioners say can help to relieve respiratory complaints, including asthma, as well as feeding more oxygen to the muscles to boost strength.
* Yoga improves posture by teaching people to relax their neck, shoulders and upper back, easing the tension that can trigger back pain. It increases flexibility, and certain postures can help to lengthen and strengthen the spine.
* Some studies suggest yoga can help with the symptoms of epilepsy, anxiety and carpal tunnel syndrome.
* According to the Journal of Psychosomatic Research, it can be an effective treatment for depression.
* Although not traditionally an aerobic exercise, one study suggests Ashtanga improves the heart's ability to use oxygen.
Types of yoga
Although it became fashionable in the late Nineties after Madonna cited it as the reason for her impressively muscled frame, yoga has been around for over 5,000 years. While the ancient Indian practice was concerned with self-realisation and spirituality rather than physical improvement, in the West, yoga is more popular as a form of exercise. According to the British Wheel of Yoga, the largest yoga organisation in the country, the best-known yogic traditions are Hatha, Ashtanga, Iyengar and Bikram, although there are numerous others, including the unorthodox aqua yoga. Each is a variation on the general theme: to direct or focus the mind without distraction or interruption.
Hatha is the yoga practised in most Western yoga classes. Developed in India in the 15th century by Yogi Swatmarama, it combines physical action or postures (asanas) with regulated breathing (pranayama) and meditation.
Beloved by Madonna, Ashtanga is a fast-paced style of yoga that has become popular in the West because it is more similar to a traditional workout than a spiritual practice. Each asana is joined to the next to create a flowing series of movements.
Created by BKS Iyengar, dubbed by the BBC as "the Michelangelo of Yoga", Iyengar is known for its use of props, such as belts, chairs and blocks, as aids in performing asanas. Its focus is the development of strength, stamina, flexibility and balance, as well as concentration and meditation.
The invention of Bikram Choudry, a former national yoga champion of India born in 1945, Bikram yoga uses a heated environment – 105F (40.5C), with a humidity of 40 per cent – to encourage sweating and stretching without injury. Choudry became the self-appointed "yogi to the stars" after moving to LA and teaching there.