The idea of “baby yoga” has an instant appeal. What could be cuter than an infant executing the one-legged “tree” pose?

But a weekday morning visit to the Sacramento (Calif.) Yoga Center’s “moms and babies” yoga class is going to disappoint anyone expecting to see babies doing “the plow,” “down-facing dog” or other advanced yoga positions.

Like most babies, these infants, ranging from 1 to 6 months old, are little bundles of potential who can’t even stand up yet, let alone do the complex balancing moves of yoga.

But Judy Guadalupe presses on, leading a class with a dozen moms whose attention is necessarily intermittent. Faced with a group that is doing everything from yoga to nursing to changing diapers at any given moment, Guadalupe maintains calm.

And she recognizes that yoga for mom and baby is mostly just for mom.

“Sometimes we do more with the babies because they’re calling for that,” says Guadalupe, a mother of three — including 4-month-old Rhia, who watches the room as Mom teaches. “But I start with the moms and get as much stretching and breathing in as I can before the babies start wanting them.”

It may not be elegant, but the fact that there is a yoga class for moms and babies is an indication that yoga — once an exotic curiosity of the counterculture — is quite mainstream.

Though its roots in an ancient philosophical system are still strong, yoga is being adapted to modern lifestyles and contemporary concerns — much to the dismay of some yoga purists.

An informal survey of yoga participants and instructors in Sacramento indicates that yoga is, above all, seen as yet another way to chase the relatively recent American ideal of getting in shape.

Studios are popping up with increasing frequency, and there are very few gyms these days that don’t offer some sort of yoga classes.

“It’s growing by leaps and bounds; I think it’s the fastest-growing group exercise,” says Sue Dunn, an exercise instructor for the past 25 years in Sacramento and a yoga teacher for 11.

Though some people say the mainstreaming of yoga as just another group exercise has drained it of some of its spiritual significance, even purists concede that the success, in whatever form, is a net gain.

“Yoga is alive,” Dunn says. “It’s meant to evolve; you take the basics and add your own thing. I take full liberty with that.”

Adding a baby to a yoga workout may seem contrary to the search for inner peace, but the moms-and-babies class instructor, Guadalupe, says that as chaotic as the classes may be, they still can benefit the mothers. That’s because the babies can perform a valuable yogic function, even though they don’t actually do much yoga.

“They’re just there, they’re so present,” she says. “In any practice, the intention is to bring ourselves to the present moment. We don’t have to go to someplace to attain enlightenment; we just have to become present. That’s their gift to us. We get to join in that enlightened moment. They are our teachers.”

This attitude — familiar to anyone who has witnessed the myriad distractions in a moms-and-babies yoga class — has a flexibility born of necessity.

Anyone accustomed to a more focused yoga class would find mom-and-baby yoga to be a frustrating experience. But it’s practical for a mother who might otherwise get no time on the yoga mat at all — and it says a lot about how the definition of yoga is being stretched.

“You don’t want to take out the spiritual aspect of yoga — the union of body-mind-spirit,” Guadalupe says. “No matter how much we want to bring it into modern life, we don’t want to lose that. It’s not just physical exercise, it is a spiritual practice.”