Exercise is good for cancer patients undergoing chemotherapy because it boosts their tumor-fighting abilities, a new study finds.

Many studies have highlighted the benefits of exercise and physical activities. A new study by researcher from University of Pennsylvania looks to add to this already long list. Researchers found that exercise is beneficial for cancer patients undergoing chemotherapy because it boosts their immunity. The study was conducted on four groups of mice with melanoma. All were given an injection of melanoma cells in the neck. During the next two weeks, two of the groups received doxorubicin in two doses while the other two groups received placebo injections. Mice in one of the treated groups and one of the placebo groups were put on exercise regimens walking 45 minutes five days a week on mouse-sized treadmills, while the rest of the mice remained sedentary.

After the two-week trial, the researchers examined the animals' hearts using echocardiogram and tissue analysis. As expected, doxorubicin reduced the heart's function and size and increased fibrosis - a damaging thickening of tissue. Mice that exercised were not protected from this damage. The mice that both received chemotherapy and exercised had significantly smaller tumors after two weeks than mice that only received doxorubicin.

"We looked, and the exercise didn't do anything to the heart - it didn't worsen it, it didn't help it," study author Joseph Libonati said in a press statement. "But the tumor data - I find them actually amazing."

Previous studies had shown that an exercise regime prior to receiving chemotherapy could protect heart cells from the toxic effects of doxorubicin, but few looked  in to whether an exercise regimen during chemotherapy could be beneficial.

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

More studies need to be conducted to gain a better understanding of this subject.

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

Findings were published online in the American Journal of Physiology.  The research was supported by the National Cancer Institute, National Heart Lung and Blood Institute, Biobehavioral Research Center at Penn, National Center for Research Resources and National Center for Advancing Translational Sciences.