WEDNESDAY, Dec. 8 (HealthDay News) -- Contrary to conventional wisdom, lifting weights doesn't cause breast cancer survivors to develop the painful, arm-swelling condition known as lymphedema, new research suggests.

There's a hint that weight-lifting might even help prevent lymphedema, but more research is needed to say that for sure, the researchers said.

Breast cancer-related lymphedema is caused by an accumulation of lymph fluid after surgical removal of the lymph nodes and/or radiation. It is a serious condition that may cause arm swelling, awkwardness and discomfort.

"Lymphedema is something women really fear after breast cancer, and the guidance has been not to lift anything heavier even than a purse," said Kathryn H. Schmitz, lead author of the study to be presented Wednesday at the San Antonio Breast Cancer Symposium.

"[But] to tell women to not use that affected arm without giving them a prescription for a personal valet is an absurdist principle," she added.

A previous study done by the same team of researchers found that exercise actually stabilized symptoms among women who already had lymphedema.

"We really wanted to put the last stamp on this to say, 'Hey, it is not only safe but may actually be good for their arms," said Schmitz, who is an associate professor of family medicine and community health at the University of Pennsylvania School of Medicine and a member of the Abramson Cancer Center in Philadelphia.

"It's almost like a paradigm shift," said Lee Jones, scientific director of the Duke Cancer Institute's Center for Cancer Survivorship in Durham, N.C. "Low-volume resistance training does not exacerbate lymphedema."

To see if a slowly progressive rehabilitation program using weights would help the arm, 134 breast cancer survivors with at least two lymph nodes removed but no sign of lymphedema who had been diagnosed one to five years before entry in the study were randomly selected to participate in one of two groups.

The first group involved light weight-lifting (starting at 1 to 2 pounds and slowly progressing) for 13 weeks under the guidance of a trainer at a local community fitness center (usually a YMCA). The women then practiced the exercises at home for another nine months.

The other group didn't exercise.

At the end of one year, 11 percent of women who lifted weights developed lymphedema, compared to 17 percent in the control group.

Among women who had undergone more drastic treatment (five or more lymph nodes removed), 7 percent of those who exercised developed lymphedema, versus 22 percent in the other group.

Although the study was designed mainly to look at the exercise program's safety, Schmitz said it was her "very strong position that it should be standard of care for breast cancer patients to be referred to a physical therapist for any of myriad arm and shoulder problems that happen after breast cancer, not just lymphedema."

"About half of survivors have arm or shoulder problems after treatment," she said.

But this study and the previous one shouldn't lead women to try the exercises on their own at home.

"There are some caveats," Jones said. "This study was in breast cancer patients who had [started] therapy [at least one year after treatment]. We don't know how the results of this might change based on women who have recently undergone surgery."

Also, "this is a really low level of resistance training," he added. "It's not where they're pushing the envelope. It's hard to know from this study what the critical threshold is. Is this resistance training [only] on the lighter side or can you go on to more moderate training?"

The study findings will also be reported in the Dec. 22/29 issue of the Journal of the American Medical Association.

More information

The American College of Sports Medicine has more on how exercise relates to breast cancer diagnosis and treatment.