Reporting from St. Louis — The students streamed into the Marbles Yoga studio -- shoulders rolling and minds calming -- as they prepared to spend an hour with their instructor inside the sun-dappled room.
For many students, the class is as much about the spirit as it is about exercise.
But for the Missouri Department of Revenue, it's strictly recreation, and the state informed yogis that studio owners and instructors must charge a 4% sales tax on class fees.
The tax, which took effect last month, has roiled the normally serene yoga world, whose supporters maintain that their pastime should be exempt from sales tax as a spiritual pursuit.
"Is this only stretching? No," said Karen Jones, who opened the Marbles studio in 2003. "I think this is just another way for the state to get money."
Many yoga practitioners say they are confused about how their ancient practice, which merges physical and mental disciplines with meditation, could possibly be equated with aerobic pole dancing or Tae Bo workouts.
But the state -- one of the few in the country to tax yoga instruction -- argues that it is not infringing on religious practices and only levying a legitimate tax on businesses.
Ted Farnen, a spokesman for the Department of Revenue, pointed out that gyms and fitness centers that offered yoga classes had been remitting the sales taxes for years, as had some yoga centers.
"It's one thing if you're going into a temple and doing yoga," Farnen said. "It's another if you're going to a studio and paying a fee to do yoga."
Most services, such as yoga classes or swimming pool lessons, are generally not taxed around the country.
Some states, however, have provisions that allow them to tax certain categories of services. In Missouri's case, some areas where sales tax can be applied are amusement, entertainment and recreation services, which include such disparate items as football tickets, gym memberships and concert admission.
Yoga managed to fly under the state's regulatory radar until a 2008 state Supreme Court decision, which ruled that fees paid for personal training services at gyms were taxable. When lawyers with the Department of Revenue were reviewing the case this fall, they determined that yoga and Pilates centers offered similar training services. That made them places of fitness and recreation, they decided, not worship.
The Department of Revenue sent out letters informing 140 yoga and Pilates centers that they should be registered with the state and start remitting sales tax as of Nov. 1.
"We only sent letters to those that charge for their yoga or Pilates services, not to temples or other religious centers that offer yoga as part of their religious framework," Farnen said.
The effect was quickly felt. Stacy Broussard, a yoga instructor who teaches at Urban Breath studio in St. Louis, said the sales tax had already begun to eat into her revenue.
"Money's already tight for people, and since this went into effect in November, I'm hearing more and more people say they're hesitant to buy blocks of classes," Broussard said. "They're coming in less frequently to class."
Yoga supporters have mobilized to fight back. Students banded together, along with instructors and studio owners affiliated with the Spirit of Yoga St. Louis, to protest the tax.
"Yoga is a spiritual practice. It's not a purchase," said studio owner Bruce Roger, a St. Louis resident who has been an instructor for 25 years. "Somehow, we need to get the state to realize that."
At Marbles, Jones glanced across her studio floor, where a dozen men and women in loose-fitting shirts and cotton pants sat barefoot and cross-legged. Flute music played softly in the background as the group meditated. Some quietly chanted as an instructor encouraged the students to focus on "movements that connect Earth to heart."
"Why would you call what we do entertainment and recreation?" Jones asked.
Yoga supporters have successfully argued their case in Connecticut and Washington state. When Washington started requiring studios to charge sales tax for their classes last year, studio owners and teachers met with lawmakers and regulators to talk about how people used yoga to achieve spiritual enlightenment.
That state's Department of Revenue reversed its decision, and yoga centers are now exempt.
"After we talked, we realized they had a point," said Mike Gowrylow, a spokesman for the department.
But it's easy to see why regulators, unfamiliar with yoga, may be seeing only how big the business has become.
Last year, Yoga Journal estimated that the field had grown into a $6-billion industry in the United States.
A number of states have tried to regulate yoga instructor programs. The states say yoga schools should have fees similar to those of other vocational training outlets, such as dance studios.