I try not to talk yoga with my friend Marty, because she's started and stopped Hatha yoga at least three times. But this time I couldn't resist. I was doing research.

"What do you think's the purpose of all those twisting poses?" I asked.

"I have no idea," she said. "Stretching my laterals?"

Who said ignorance is bliss? So many smart people just think of yoga as what the poses look like on the outside, focusing on the external form: Triangle, Half Moon, Down Dog.

Just as important, more important really, is what is going on inside your body as you relax into each pose, creating space with your breath, directing energy in ways that restore muscle tone and balance.

WHY TWIST? When you do a twist, you are giving many vital body parts a good squeezing. Followed by a good soaking.

Your kidneys, your adrenals, your liver ... different postures work different areas, but the one thing all twists have in common is that they flush out the stagnant blood and bring in the fresh, healing blood.

This revitalizes your organs, glands, muscles and joints. A few twists a day really can help keep the doctor away ... from your bank account, for instance.

Twists bring oxygen and vital fluids to your spine, your hips and your pelvis. Without your help, as the body ages, they shrivel and get stiff and painful from dryness and disuse.

LEARN HOW. So now you know why you should do twists. Next you need to learn how. A sensitive, experienced yoga teacher is best for that. Over-twisting must be avoided, so it's your job to tune in to your body and respect your limits. Every twist isn't safe for everyone. It's one thing to go to your edge; it's quite another to push through pain. Never do that! And don't let your well-intentioned yoga teacher do it to you.

TRY THIS NOW. Now that you're revved up about twisting, why not give it a try? Here's how to do a seated spinal twist from a useful book by Susan Winter Ward called "Yoga for the Young at Heart: Accessible Yoga for Every Body":

"(This spinal twist) lubricates and nourishes the spinal column, increases elasticity of the muscles and ligaments of the spine, balances the nervous system; prevents backache, massages internal organs, toning liver, kidneys and spleen. Aids digestion and elimination."

Amazing! You can't say that about a game of tennis.

WHAT TO DO. "Sit on the floor, legs out in front of you. Bend your left knee and place your left foot on the floor to the outside of your right thigh. If you feel pain, don't continue. If you continue, ease into the twist slowly, mindfully, feeling your way."

Ward continues: "Inhale deeply as you extend your right arm out to the side, shoulder height.

"Exhaling, bring it around your left knee, holding your knee with the inside of your elbow. Draw the right side of your rib cage toward your inner left thigh.

"Inhale as you raise your left arm up and overhead. Keep your back flat and your heart lifted.

"Exhaling, lower your left hand to the floor behind you, as close to your tailbone as you can. Press the palm of your hand into the floor, lengthening your spine."

More instruction:

"Be sure that both sitting bones stay squarely on the floor.

"Inhale as you lift through the crown of your head and exhale as you rotate your chin to gaze over your left shoulder.

"Press against the floor to lengthen your spine with each inhalation and gently twist a bit more - if possible — with each exhalation, using your front arm and leg as a point of leverage.

"Take three to five long, slow inhalations and exhalations.

"Come out of the pose gently, inhaling as you raise your left arm overhead and exhaling as you bring your body around to face forward again.

"Take a few breaths, and repeat on the other side."

Twists are part of yoga because squeezing-and-soaking is so good for your body. Once you understand that, you'll find a zillion variations to try, on the floor, in a chair, standing at your desk.

The late, great Chubby Checker on your iPod is optional but terrifically inspiring.

ENERGY EXPRESS-O! THE BLISS OF TUNING IN

"Yoga is almost like music, in a way; there's no end to it." — Sting

Marilynn Preston — healthy lifestyle expert, well being coach and Emmy-winning producer — is the creator of Energy Express, the longest-running syndicated fitness column in the country. She has a website, marilynnpreston.com, and welcomes reader questions, which can be sent to MyEnergyExpress@aol.com. She also produces EnExTV, a digital reincarnation of her award-winning TV series about sports, fitness and adventure, for kids of all ages, at youtube.com/EnExTV and facebook.com/EnExTV. To find out more about Preston and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.