Chemotherapy, while potentially lifesaving, is notoriously draining on the human body. It can make patients feel fatigued, nauseated, and downright lousy. But a new study by researchers in the School of Nursing and the Perelman School of Medicine suggests that patients who push past the malaise and do some low-impact exercises during their chemo regimen might help their cancer drugs work better.

Joe Libonati, an associate professor at Penn Nursing and director of the school’s Laboratory of Innovative and Translational Nursing Research, led the study, which was originally intended to see if exercise could lessen the negative effects that chemotherapy can have on the cardiovascular system.

“Going in, I was interested in what exercise was doing to the heart,” Libonati says. “I never even dreamt it was going to affect the tumor.”

The research, which appears in the American Journal of Physiology, used a mouse model of melanoma and tested a common cancer drug, doxorubicin. Though effective at treating a variety of types of cancer, one of doxorubicin’s more serious side effects is that it damages heart cells. In the long term, this damage could lead to heart failure.

“The immediate concern for these patients is, of course, the cancer, and they’ll do whatever it takes to get rid of it,” Libonati says. “But then when you get over that hump, you have to deal with the long-term elevated risk of cardiovascular disease.”

Previous studies have found that exercise either before or after chemotherapy has beneficial health effects, but few studies have tested the effects of exercise during chemo. The research team set up an experiment in which mice with melanoma were divided into four groups: One group was untreated, a second received doxorubicin, a third received doxorubicin and was put on treadmills to walk 45 minutes, five days a week, and the last group had the same exercise regimen but was not given the drug.

After two weeks, somewhat unexpectedly, the researchers found that the exercise regimen did not protect the mice’s hearts from doxorubicin’s toxicity; their heart tissue showed the same signs of damage, or even more, as the hearts from mice that did not exercise.

But this pairing of exercise and chemo did have a big benefit: It shrunk tumors more than the chemo did alone.

Libonati says there is still much to learn, but it could be that exercise increases blood supply to the tumor, effectively channeling more drug to the cancer. If this is the case, doctors may be able to use smaller doses of chemotherapy, lessening the chance of negative side effects.

“People don’t take a drug and then sit down all day,” Libonati says. “Something as simple as moving affects how drugs are metabolized. We’re only just beginning to understand the complexities.”