But doctors are recommending that they prioritize it to increase their chances of beating breast cancer, improving their mood and making sure cancer doesn't return.
"The largest study to date followed survivors over five years and found that one to two hours of brisk walking per week was associated with 40 percent lower risk of death overall compared with those who were less active," said Susan Brown, managing director of health and mission program education at Susan G. Komen Breast Cancer Foundation.
A 2011 meta-analysis of studies found that the mortality rate for breast cancer was 34 percent lower for women who were very active when compared with women with breast cancer who weren't active.
Still, a 2013 study found that breast cancer survivors aren't meeting national exercise recommendations.
Even though much of the research has focused on the long-term effects of exercise, many of the results can be felt right away, said Julie Everett, a physical therapist at Johns Hopkins Hospital in Baltimore.
"It can increase your energy, which sounds a little backward," Everett said. "You're expelling energy to gain more. If you increase your calorie burn, it can decrease the fatigue."
She said that exercise also combats depression, which is common with cancer patients.
The key is figuring out how to get back into exercising — or even to start a fitness routine from scratch — after a woman is undergoing breast cancer treatment or has had a mastectomy.
Most people who have had a lumpectomy or minimal surgery should be able to start an exercise regimen within six weeks, after getting approval from their doctor, though those who have undergone a more extensive surgery may have a longer wait, said Lidia Schapira, assistant professor of medicine at Harvard Medical School and staff oncologist at Massachusetts General Hospital.
If the person undergoing treatment is fit and already used to exercising before she was diagnosed, she can continue her routine, simply running a little slower if she was a runner or lifting weights that are a little lighter, Schapira said.
Everett said she recommends beginner yoga and tai chi for breast cancer patients because both forms of exercise will start to stretch the patient's arms, targeting the areas that were affected through the treatment.
Regardless of the type of exercise that patients choose, Everett said that the key is to not exercise too ardently.