WASHINGTON (AP) - For many dancers, swanlike grace comes at a price - painful back injuries that could have been avoided if they had worked out right.

And it may take a new type of specialist - someone who combines sports medicine and the arts - to treat them, a study said.

``Dancers spend a lot of time building up their leg muscles, but much less time building up their trunk,'' said Dr. Lyle J. Micheli. He treats dancers of the Boston Ballet at the Sports Medicine Clinic in Children's Hospital in Boston. He also was lead author of an overview article on dancers' back injuries in the medical Web site MedScape.

Like young gymnasts, dancers risk microtears to the vertebrae in the lower spine, the article said. The injuries result largely from repeating dance positions that bend the spine far backward, Micheli said.

One such position is the arabesque, in which the dancer balances on one leg while extending the other high to the rear. It can produce excessive arching of the low back, Micheli said.

Choreographers are not going to give up the arabesque or similar positions just to make life easier for dancers, however. So dancers will have to adjust, said coauthor Ruth Solomon, a professor of theater arts and dance at the University of California, Santa Cruz.

And adjusting is within their power, Solomon said: ``A body is very capable of doing things if it is trained well.''

Training will require dancers to pay more attention to their pelvic girdles, Solomon said. Stronger trunk muscles can take some of the workload off the muscles that control the rear of the spine, she said. ``The back and the pelvis move as a unit, so there is no excessive force right at the base of the spine,'' she said.

Solomon focuses on strengthening muscles such as the psoas, which stretch between the front of the lower spine and the upper leg at the front of the hip. To do this, she has dancers do leg lifts, bringing their legs to their chests while lying on their backs with their weight balanced just above their tailbones.

The spine is in a curved position during this exercise, and enhancing the curve is something that Solomon wants dancers to focus more on. So does Barbara Harris, a trainer and rehabilitation specialist for the Boston Ballet.

A normally curved spine acts like a spring, absorbing impact from dance movements, Harris said. But dancers think a straight spine is better - ``it makes them look very lifted and very long,'' she said.

The ``lifted'' look, with a straight back and neck, and pelvis tucked under the back, makes dancers seem to float as they move, Harris said. However, dancers can get the same look with less risk to their backs simply by keeping the pelvis in a neutral position, neither tilted forward nor back, she said.

Those who don't prepare their backs properly may wind up at the sports medicine clinic and at rehab. At the clinic, they may get X-rays and bone scans. The scans have the advantage of picking up tiny tears before they get big enough for X-ray spotting, when the injuries are harder to heal, Micheli said.

At rehab, Harris works with a Pilates-based system of flexibility and strengthening - a method that often is familiar to dancers. She also focuses on teaching them how to recognize and foster good back alignment.

Almost all dancers can dance after treatment, Micheli said. But older dancers may not heal as easily, he said - like older athletes, they may return to their activity, but must recognize they will have to play with pain. Research thousands of health terms, drugs, and diseases