Breast cancer survivor Donna Dunning started coming to a yoga class more than four years ago, right after her diagnosis.

"I came when I could barely walk... often had to leave the class two or three times," said Donna Dunning.

The emphasis here is on gentle movements. Instructor Laura Yon-Brooks gears the class to the needs of each patient.

"Bodies don't heal well under stress and having cancer is stressful. This is our chance to help relax them and help decrease that stress so they can heal better," she said.

"We know that a lot of women with breast cancer will practice yoga and they find it relaxing or as something enjoyable, but it's not really been tested, and we want to see what's the effect of yoga on which things as quality of life, fatigue and weight," said Dr. Anne McTiernan.

This will be the first study to look at the effect of yoga on weight gain in breast cancer patients. Past research shows women who are overweight or obese or who gain weight after diagnosis may have poorer survival rates as well as an increased risk of recurrence.

All Donna knows is that yoga made a huge difference in her life.

"It helped make me feel like there were other people in as bad shape as I was. It frequently just gave me courage to go on the next day," she said.