About 80 percent of women who took up twice-a-week weight training saw improved scores on a quality-of-life survey, researchers said in a study to be published in an upcoming issue of the journal Cancer.
In contrast, 51 percent of participants in a control group did.
The physical and psychological benefits of exercise are well-documented. But this study is the first to apply scientific methodology to looking at how weight-training helps women who have had breast cancer.
"This may seem like common sense to most folks, but there's really been no literature or science where researchers tried to quantify and verify the effect," said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society.
Researchers recruited 86 women from the Minneapolis-St. Paul area in late 2001 and early 2002. Each of the women had completed successful treatment of breast cancer within the previous three years.
Half the women were assigned to an exercise group. For three months they met twice a week with personal fitness trainers to develop a weightlifting regimen. They were then encouraged to follow it for another three months.
The second group had no such regimen.
Researchers asked women in both groups a series of questions about physical well-being, marital happiness, sexual activity and other aspects of life.
Women in the exercise group had a modest improvement over members of the non-exercising group, Lichtenfeld noted.
However, the women in the exercise group said they felt they had more strength, speed and self-confidence as a result of the workouts. It appears the weightlifting helped them regain a feeling of control of their bodies, researchers said.
The more the women improved on bench press, the better they said they felt overall. That may be because breast cancer treatment can reduce the ability to lift and carry things, said Kathryn Schmitz, a University of Pennsylvania researcher who co-authored the study.
The study also tried to observe weight training's effect on depression. The researchers didn't measure any significant effect, but they said that might be because such a small number of women were deemed to suffer from depression at the outset of the study.
By Mike Stobbe