Millions of Americans get into mental, spiritual and physical shape through yoga, and a new study suggests regular yoga sessions can also help people with low back pain find relief, with benefits lasting several months.

Researchers in Washington state and Oregon found that adults with back pain that is moderately impairing experienced less pain and better functioning after taking yoga classes.

In the study, a total of 228 adults either attended 12 weekly yoga classes, did stretching exercises or read a book that provided information on exercises and other ways to reduce back pain.

When the three interventions were compared, yoga classes and stretching exercises were equally effective and were better than the book at providing pain relief and improving overall functioning.  In many cases, the improvements persisted over several months.

“I think it adds another piece of evidence that exercise is valuable for people with chronic back problems,” said Dr. Richard Deyo, a study co-author and professor of family medicine at Oregon Health Sciences University in Portland.  “It suggests yoga is a good option, but not necessarily the only one.”

Yoga’s benefits, the authors found, were largely physical, resulting from strengthening and stretching of the back and leg muscles.

About twice as many people who took yoga or stretching classes reported using fewer pain medications compared to participants who used only the self-help book.

“This suggests exercise can be a substitute for medication and reduce its use,” said Deyo.  Pain medication, he said, can often have side effects and may not last long.

A 2009 study in the journal Spine also found benefits associated with yoga in people with chronic low back pain.   Participants who took six months of classes in Iyengar yoga, which uses objects such as belts and blocks to help align the body properly, experienced significantly less pain, fewer depressive symptoms and less functional disability compared to study participants who used other types of therapies.  Those who took yoga classes also used less medication.

As long as yoga classes are geared toward this type of stretching and strengthening and the exercises can be modified if people experience pain, Deyo recommends them.

“Exercise is valuable, but the only way it’s going to work is if people are doing something they want to do and enjoy it,” he said.

In an accompanying comment, Dr. Timothy Carey, professor of medicine at the University of North Carolina-Chapel Hill, said exercise should become a regular component of treatment for low back pain.

“We physicians should refer our patients for exercise, practitioners should work to standardize treatments, and payers should encourage these treatments through minimization of co-payments for therapies that have both effectiveness and modest cost,” he wrote.