A new year means new resolutions, such as finally getting in shape.

For many, that means checking out the latest exercise craze. And this year, the latest craze turns out to be one of the oldest: yoga.

The ancient mind-body-spirit practice has become the “in” way to work out.

Yoga mats, incense and flare-leg knit pants have become the norm in many gyms, and such poses as “up dog,” “down dog” and the “camel” are familiar to many practitioners.

Yoga attracts both 20-somethings searching for spiritual enlightenment and Baby Boomers looking for nonsurgical ways to ease their aching joints. An estimated 20 million Americans practice yoga, according to Yoga Journal.

This ancient practice combines meditation, stretching and breathing exercises, and experienced its first wave of popularity in the United States in the late 1960s as a drug-free way to get high. It emerged again in the last decade or so, catching the attention of celebrities such as Sting, Madonna and Mariel Hemingway.

“I’ve been doing it for 40 years — everybody thought I was crazy,” said Diane Hatfield, owner of Bikram Yoga South Jersey. “It took a few movie stars to do it and people just realize how good it was.”

That said, here’s a brief guide to the new twists on this exercise classic.

HOT YOGA

Officially known as bikram yoga, hot yoga differs from traditional yoga practices, because classes are held in rooms where the temperatures have been up to 105 degrees. After twisting themselves into a series of 26 poses, students emerge drenched in sweat. Fans swear by it, saying the heat helps the body dispense of toxins, while also loosening muscles and collective tissue, making bodies more limber.

“Yoga comes from India and India is hot,” Hatfield explained. “We should have been doing it this way all the time.”

The practice is considered controversial by some who point out that it can cause dehydration and heat exhaustion.

“If you’re a middle-aged person with undiagnosed cardiovascular disease, you probably don’t want to do that,” said Trisha Lamb Feuerstein, director of research for the Yoga Research and Education Center in Santa Rosa, Calif.

ASHTANGA

Madonna credited a combination of pilates and ashtanga yoga for the sinewy muscles she sported during her Drowned World Tour. Ashtanga, which is often recommended for people hoping to improve their performance in other sports, involves synchronizing deep breathing with a progressive series of postures.

“You link posture to posture with a very deep back of the throat breath,” explained Amy Gordon, who specializes in ashtanga. “It builds heat and also soothes your mind.”

KRIPALU

Kripalu is a gentle, introspective practice in which much emphasis is placed on breathing techniques and releasing emotional blockages. Initially, practitioners concentrate mainly on poses and deep breathing followed by emotional work. In the third phase, practitioners perform a series of spontaneous poses.

“We tend to be a little less dogmatic than other schools so that makes us understandably difficult to describe,” said Cynthia Geesey, director of Stretch thru Stress in Philadelphia.

But, “we’re going to move slower than something like power yoga, so it’s going to be easier to stay with us and what’s happening,” she added.

CLASSICAL YOGA

Classical yoga draws a little bit from all the major disciplines, and is highly recommended for beginners.

“It incorporates all the limbs of the tree of yoga,” said Sharon Kind, an interfaith minister who also teaches yoga. “We do mantra. We do asana, which is the physical practices; pranayana, which is breathing practices: and we do a meditation.”

“It has a little bit of this and a little bit of that,” she said.