In fact, McCaochan of Royal Oak, Mich., wants to develop yoga at the wall, as she calls it, as a practice all its own.

The author of the book "Yoga at the Wall; Like Stanzas in a Poem," (In the Company of Women, $19.95), McCaochan says the benefit of using the wall is getting a better understanding "of where your body is in space." She calls it a "conversation with your body."

"When I say turn your toes to the front of the room, maybe 75 percent of people get that," she said. "Some people will not get it. They're not turning at all, or they think their foot is straight, but it's not. That's the sort of body awareness the wall helps with."

Line up on a wall, and it's suddenly clear whether your shoulder blades are hunched. Or if your heels are aligned. It's an awareness that can carry over to regular mat work.

"A lot of people don't have the sensitivity of their own movements," McCaochan said, "so it's not until they press against the wall. Then they say, 'Ah, that's what you're talking about.'"

The poses McCaochan, 63, features in wall classes would be familiar to regular yoga practicers.

For instance, the ever-popular downward dog is called wall dog in wall yoga. Instead of bending at the waist and leaning forward with hands and feet on the floor, forming your body into a V, in wall dog you place your arms on the wall parallel to the floor. When you bend down, it becomes more of a stretch for your back and legs.

"Very often I feel the correct alignment better on the wall," said 62-year-old Ken Axelrod, from Bloomfield Township. "You come into the poses a different way. You get better stretches against the wall."

Axelrod, who has practiced yoga for four years, said he can do poses in wall class he'd never be able to do otherwise — particularly inversions, where his legs are positioned on the wall and his back or shoulders on the floor.

Debra Darvick, 53, of Birmingham, Mich., said McCaochan's classes have changed her life.

"It's the philosophy that whatever challenges are there, to work with them physically, not against them," Darvick said. "A good example is that in yoga, you get yourself centered before you extend your limbs. That's good practice in regular life, to ground yourself before you extend yourself."

And it's apparently good for the body, too. Darvick, who has been doing wall yoga for four years, said her doctor told her recently that her heartbeat sounds like a teenager's.