Geri does it. And also Madonna. As does Sting. Celebrities aside, yoga, the 5,000-year-old Asian system of gentle exercise, light meditation and breathing techniques is, for many in the West, a popular and harmless way to keep fit and remain calm amid the multiple pressures of modern life. In Britain alone, more than 3,600 people belong to the British Wheel of Yoga, the national governing body for yoga which defines the pursuit as a Sanskrit word meaning “union between mind, body and spirit” and a “philosophy”. Its most popular version in the West, hatha yoga, takes the form of classes offering stretch and flex exercises, meditation and “breath awareness”.

It all sounds fairly innocuous. Yet for some Christians all forms of yoga are spiritually suspect, a subtle form of Hindu worship, replete with danger for the unwary enthusiast.

Laurette Willis, an American exercise instructor, taught and practised yoga for 22 years before her conversion to evangelical Christianity. “I don’t think it is possible to subtract the spiritual element from yoga,” she says. “Webster’s Dictionary defines yoga as ‘an ascetic Hindu discipline’ and yoga postures derive from gestures of offering traditionally made to Hindu gods, while the pranayama breathing techniques used involve a manipulation of energy that, according to Ephesians 2:2, Christians are not supposed to do.”

Willis believes this to be true of all yoga, even hatha, which she views as a stepping stone to other, more explicitly spiritual versions. “In many normal yoga classes, the teachers will say the word Namaste, which means ‘I bow to the God within’,” she says.

For Willis, yoga’s biggest spiritual danger is that it acts as a gateway to New Age spirituality. “A large number of the people I met in the New Age movement came through the door of yoga. I was looking for God and didn’t see it in churches or religion, which I didn’t know then was about a personal relationship with Christ. I was spiritually hungry but if someone is not a Christian, yoga definitely leads them away from Christ.” Willis claims to have had “some profound psychic experiences”, including “astral travelling” through meditations at the end of yoga classes. “Having done that, I realised there is a spiritual realm about which we know very little. Yoga takes us up to that realm, but that relaxation is different from the peace that we are promised by Jesus Christ. It’s a counterfeit.”

Willis is not alone in linking yoga to the New Age. Earlier this year, the London-based Roman Catholic exorcist Fr Jeremy Davies wrote in his bestselling Catholic Truth Society pamphlet Exorcism: Understanding Exorcism in Scripture and Practice: “The thin end of the wedge (soft drugs, yoga for relaxation, horoscopes just for fun and so on) is more dangerous than the thick end, because more deceptive — an evil spirit tries to make his entry as unobtrusively as possible.”

Dr Ali Malik, the editor of Yoga Magazine, disagrees. He says Christian fears of yoga are based on a fundamental misunderstanding of the subject. “Yoga is so ancient it is impossible to link it to any religion as it pre-dates even many of the world religions. The origins of yoga can be traced 4,000 years ago to the Indus Valley region in Pakistan, where stone seals depicted deities sitting in yogic postures,” he says, adding that the first yoga manual, the Yog Sutra, was compiled approximately two centuries before Christ. While recognising that Hindu sacred texts such as the Bhagavad Gita contain references to yoga, Malik says the practice has evolved over time. “Today we have over 100 styles of yoga tailored to differing needs. Some styles of yoga are religious-based; many are not. There is no text in yoga that states you must believe in this or that. There is a spiritual side to yoga. Classical yoga speaks of the Supreme Being, but it is not a pantheistic model, but a monotheistic concept. Serious practitioners will undertake further study into the spiritual side of yoga. Everyone according to yoga philosophy is inherently spiritual. The spiritual approach to yoga is vast, for instance ethical behaviour is encouraged as it has a major impact on our environment. Yoga is peaceful, a blueprint for living. It is not dogmatic or religious in its content.”

The main aim of yoga, Malik says, is to bring inner peace. “Techniques such as the asanas (postures), pranayama (breathing), meditation, for example, are merely tools to awaken that inner state of peace and fulfilment. Yoga means to still the chattering of the mind. A disturbed mind causes problems to the physical body.”

This approach is espoused by Swami Ramdev, an Indian yogi whose classes are followed by more than 120 million worldwide on AsiaTv. Thousands more attend outdoor classes at his institute in north India, billed as the largest yoga centre in the world. “Yoga is a medical science,” he says. “It brings those who follow it health, wealth and peace. Christians who practise it will become better Christians as it will make them more at peace.”

Willis argues that yoga offers a “false peace”. “There is a difference between peace and numbness. Yoga numbs people.” She has little time for Christian Yoga, a movement highly popular in the US which unites Christ-centred meditation with yoga movement. ’This is an oxymoron,” says Willis, who has devised her own Christian alternative, where exercise poses with titles such as “standing Cross” or “the harp of David” mirror Christian scripture and belief.

For, Malik, however, Christian distrust of yoga is based essentially on irrational fear of a non-Western approach to medicine: “The problem in the West is that it feels threatened by anything ‘different’ which doesn’t fit in nicely with that ‘orderly’ approach. There is no doubt that practice of yoga brings numerous benefits and certainly brings great advantages to people who are experiencing physical and mental ailment.”