A good stretch

Yoga is more than just striking a pose. But how you strike that pose is nonetheless critical. Maintaining correct form is essential not only for building a solid yoga practice but also because improperly doing the same yoga poses repeatedly — even the most basic ones — can lead to strains, sprains and chronic aches.

Yet it's easy to go awry. Many popular classes are overcrowded, making it difficult for teachers to correct every swayed back and hunched shoulder. Even in smaller groups, a misaligned leg can easily go unnoticed. And then there's the fact that less experienced students sometimes try to emulate more practiced ones, over-stretching muscles or getting joints out of alignment in the process.

As for doing yoga only at home with no supervision? That can be a recipe for disaster.

"Yoga is really about getting to know your body," says Christine Burke, co-owner and director of Liberation Yoga in Los Angeles. "A lot of us don't have that awareness of what something is supposed to feel like when it's right."

That can make going from bad form to good form sometimes feel uncomfortable, she says. Occasionally the body must get used to the new position before the resulting aches and pains go away.

We talked to three yoga teachers about the most common mistakes students make while doing basic poses. They explain the potential harm and offer easy ways to correct improper form.

Christine Burke

Co-owner and director of Liberation Yoga, Los Angeles

Downward-facing dog: The body bends at the hips in an upside-down "V," with arms straight, hands on the floor and heels pressing toward the floor. The head is aligned with the spine.

Don't: Drop or hang into the shoulders. People do this in an attempt to truly stretch, but it prevents the joints from stacking properly and puts stress on the shoulders, elbows and wrists.

Do: Lift the shoulders and slide the arms forward a little, taking some of the pressure off the shoulders. Also, open the hands and press them into the floor. (Curling the fingers up will put the pressure right back into the wrist.)

Warrior I: The body is in a modified lunge position, with the front leg bent and the back leg straight. Arms are straight and parallel, reaching upward, palms together.

Don't: Push the knee too far over the ankle. When the knee goes too far forward, the knee joint is in a precarious position. This puts strain on the kneecap and the knee joint, possibly causing pain. It's like building a structure — you don't want to have boards on an angle; you want to have a square foundation.

Do: Make sure the ankle is under the knee so that the leg is in a straight line perpendicular to the floor. To balance in this pose, push into the back leg. This is easier to do if the front knee is directly over the ankle. The back leg tends to get underused, and it can sometimes take you too far forward.

Warrior II: Legs are as in Warrior I, but the arms are outstretched at the sides, perpendicular to the sides of the body.

Don't: Let the shoulders rise toward the ears. The shoulders are a common place to hold tension, and people sometimes tend to let them move up when they're tired. But holding the shoulders up can shorten the trapezius muscle (which extends from the base of the skull across the shoulders and down the back) and can cause a bit of spasming.

Do: Concentrate on using the rhomboid muscles (back muscles that connect the shoulder blade with the spine) and the core to prevent the tension from riding up into the shoulders. This is a challenging posture and also an endurance posture. Because the core is at the center of the body, maintaining the right form is grounding — helping lift through the chest and promoting proper alignment of the spine.

Plank: Facing the floor, the body is elevated and supported by the feet and arms, with the arms straight, as if starting a push-up.

Don't: Lift your bum, especially if you're not feeling that strong in the upper body. It puts extra pressure on the shoulders, elbows and the wrists. Most likely the shoulders will be ahead of the wrists, a position that doesn't use energy efficiently and is unnecessarily exhausting.

Do: Drop into a gentle diagonal from the shoulders to the heels. This employs the core muscles, taking pressure off the shoulders. It also stacks the elbows over the wrists and the shoulders over the elbows, so excess pressure isn't on any of the joints. There's an even dispersion of energy. Because the plank is often used to connect one pose to another, the proper form will make transitions easier, without unnecessary shifting.

Candace Morano

New York-based yoga instructor and educational kinesiologist

Seated pose with pranayama: Knees are bent, with one leg placed over or in front of the other. The pose is done with pranayama, or breath control.

Don't: Sit with the shoulders rounded forward, which collapses the area around the rib cage. That can affect the ability of the lungs to hold a lot of oxygen and to get air deeper into the lungs. Think of a bent straw — it doesn't move liquid as well.

Do: Feel the front of the body lengthening — and the sides too, from waistline to armpits and from lower back to skull as you breathe in. Breathing is like pouring water into a glass; the body is a container, and the breath goes into that cylinder. In some exercise classes, the abdominal muscles are strengthened by doing a crunching motion. But in yoga, the abdominal muscles are strengthened by lengthening them. This also takes pressure off the back muscles, helping prevent back pain caused by a weak center.

Standing forward bend (also called a standing forward fold): Feet are together as the torso and head bend forward toward the legs.

Don't: Hyperextend the knees. That puts pressure on the hamstrings (the muscles at the back of the thigh) and the Achilles tendon. There's a connection from the Achilles all the way up to the spine, so hyperextending almost puts a lock on the energy flow. This can lead to more tightness in the lower back and strain on the knee joints.

Do: Bend the knees a little bit. This helps draw the hips forward over the ankles. Sometimes that will make people feel as if they're falling forward, but it also engages the muscles in the front of the thigh, in turn lengthening the front of the thigh muscle (the quadriceps) and then the hamstrings. This creates more of a balance.

Anthony Benenati

Founder of City Yoga, West Hollywood

Chaturanga: The torso and legs are parallel to the ground and are supported by the feet and hands. Arms are bent and hands are tucked under the chest.

Don't: Let the shoulders dip past the elbows when you bend your elbows and lower down in this pose. Letting the shoulders go lower than the elbows can cause the back to round. It also puts the arms out of alignment and forces weight onto the wrists. That can immediately cause shoulder and wrist pain.

Do: Engage the back muscles, keeping the shoulders at the same height as the elbows. The shoulders should be back, the hands strong and the chest lifted. While on the floor, the hands should be relaxed and as strong as any other part of the body that touches the ground. Engage the fingers and use the hand and forearm muscles.

Cobra: With the body lying on the floor, the legs are stretched back with thighs and feet touching the floor. Back is arched and chest is lifted, supported by the hands, which are underneath the shoulders.

Don't: Let the upper and lower body move toward each other. The cobra is a backbend, but the upper and lower body should be moving in different directions. Otherwise, the lower back will compress, causing immediate pain.

Do: Root the legs on the ground and move the chest away from the pelvis. Backbends are supposed to be extending, so the hips shouldn't be pushed toward the chest; instead, the legs should be extended away from the chest. The shoulders should be back, with the backbend felt in the middle and upper back.