Hamilton, USA - When Cathy Chadwick instructed her three yoga students to move into warrior position, she did not remind them to watch their alignment or focus on their breath. Instead Ms. Chadwick urged them to concentrate on the affirmation each made at the beginning of class after she read aloud the prayer of St. Theresa of Avila.
"Good Christian warriors," Ms. Chadwick softly said as the women lunged into the position.
Ms. Chadwick is one of a growing number of people who practice Christian yoga, incorporating Biblical passages, prayers and Christian reflections. Occasionally, teachers rename yoga postures to reflect Christian teachings or, as Ms. Chadwick did with warrior position, include religious metaphors.
Some, like Ms. Chadwick, had taken yoga classes and enjoyed the physical benefits but were uncomfortable with the fact that yoga is a Hindu practice. Others said that yoga allowed them to connect with their spiritual sides, but that it should be filled with their own religion.
"I feel more comfortable practicing yoga in conjunction with my faith," said Ms. Chadwick, whose class meets at Christ Church in this town 30 miles north of Boston. "When I practiced yoga before, I felt I was being asked to open up to a deity, and that deity to me is a Christian deity."
A similar movement is taking place in Judaism, with teachers merging teachings or texts into yoga classes. Many who take part said Christian and Jewish yoga made the physical discipline more accessible to those otherwise unwilling to take a class for religious reasons.
Centers that teach only Christian or Jewish yoga are popping up across the country. Most classes teach hatha yoga postures, gentle enough to be performed by novices.
But critics of the alterations say that yoga is inherently Hindu, and that it is not possible to truly practice it without embracing that element.
"There is an element of superficiality or hypocrisy there," said Subhas R. Tiwari, a professor of yoga philosophy and meditation at the Hindu University of America in Orlando, Fla. "To try to take Hinduism or aspects of Hinduism outside of yoga is an affront. It's an act of insincere behavior."
Douglas R. Groothuis, a professor of philosophy at Denver Seminary, said that yoga was a Hindu practice structured to help people attain a higher spiritual state within, and that was incompatible with Christian teachings.
"I don't think Christian yoga works," he said. "It's an oxymoron. If it's truly Christian, it can't be truly yoga because of the worldviews."
The Vatican has also expressed misgivings about yoga. In a 1989 letter, Cardinal Joseph Ratzinger, head of the Congregation for the Doctrine of the Faith, who is now Pope Benedict XVI, said practices like yoga and meditation could "degenerate into a cult of the body."
Even so, the number of people who practice Christian yoga is rapidly growing, said the Rev. Thomas Ryan, a Paulist priest in Manhattan and editor of "Reclaiming the Body in Christian Spirituality."
Father Ryan, who developed many of the Christian yoga techniques adopted by others, said yoga postures were vehicles for people of all faiths to invite spirituality into the heart and body.
"It is better seen as a hardware to which one brings his or her own software and one's own faith understanding to transform the practice from within, so the intention is always critical," said Father Ryan, who is assembling a database of Christian yoga instructors.
Myriam Klotz, a reconstructionist rabbi and co-founder of the Yoga and Jewish Spirituality Teacher Training Institute at Elat Chayyim, a Jewish spiritual retreat center in Accord, N.Y., said she used yoga as a way to integrate the body into Judaism.
"I would like the Jewish experience to be more full-bodied," Rabbi Klotz said, "and yoga is one of the best ways I have found to live a more full-bodied life. I don't mean to create a new Judiasm. It's being respectful of the yoga tradition and integrating the Jewish tradition and letting them befriend one another."
For example, if Rabbi Klotz is teaching about the Jewish principle of people being grounded on Earth but stretching their souls up, she has students stand in mountain pose as a physical expression of that teaching.
Stephen A. Rapp, a Boston yoga teacher, developed Aleph-Bet yoga, a series of postures meant to represent Hebrew letters. Mr. Rapp said he saw the connection between poses and letters one day when, after he had shown his children yoga postures, he watched a scribe repair a scroll at synagogue.
For example, Mr. Rapp expresses the Hebrew letter bet in the posture Dandasana, where one sits on the ground with legs and arms straight out in front. Mr. Rapp believes postures are part of a physical yoga system into which spirituality is incorporated.
"It's the thinking about the shape and thinking about the symbol and what it means while also doing this form of exercise," he said. "It gives you a focus, an intention. You really have to have the intention correct in yoga."
But Swami Param, head of the Classical Yoga Hindu Academy in Manahawkin, N.J., said that if people could not acknowledge the Hindu element of yoga, they should not bother studying it.
"As Hindus we have no problem studying other religions," Mr. Param said, "but we give them the respect they deserve."