Rather than undergoing expensive and often extremely unpleasant treatments, Fox News reports that a recent animal study suggests that regular exercise may be one of the most effective tools in battling cancer.

Researchers determined that mice that spent the majority of their free time on a running wheel were 50% more likely to experience shrinking of tumors than their stagnant counterparts.

“It is known that infiltration of natural killer (NK) immune cells can control and regulate the size of tumors, but nobody had looked at how exercise regulates the system,” remarked senior study author Pernille Hojman of the University of Copenhagen.

By injecting mice with adrenaline to mimic the increase caused by exercise, researchers saw that NK cells targeted tumors. The other group of mice depleted of NK cells showed that even with exercise and other immune cells, tumors retained steady growth.

The correlation between adrenaline-dependent mobilization of NK cells and the infiltration of tumors was found to be an immune signaling molecule called IL-6.

They determined that adrenaline initiates IL-6 sensitive NK cells, then the IL-6 molecules guide immune cells to the tumor.

“That was actually a big surprise to us,” continued Hojman. “In this study we show that the exercise-induced IL-6 seems to play a role in homing of NK cells to the tumor and also in the activation of those NK cells.”

However, while exercise might be key in thwarting the growth of cancer cells, it may not be quite as beneficial to other aspects of physical well-being in patients.

According to the Doctors Lounge, a recent study found that exercise didn’t show significant improvement in physical functionality in women suffering from advanced breast cancer.

Researchers from the Dana-Farber Cancer Institute in Boston examined 101 randomized patients with metastatic breast cancer participating in 16 weeks of moderate-intensity exercise intervention. It evened out to about 150 minutes of exercise per week.

Meanwhile, 42% percent of the participants were actually undergoing chemotherapy during the study.

The researchers found no significant relationship between regular exercise and improved physical functionality.

Even though exercise during treatment may not have an enormous benefit for current breast cancer patients, the researchers acknowledge that regular exercise is very beneficial for the one in eight U.S. women who will be diagnosed in the early stages of invasive breast cancer in her lifetime.

“Given the significant benefits of exercise in women with early-stage breast cancer, more work is needed to explore alternative interventions to determine whether exercise could help women with metastatic disease live more fully with fewer symptoms from disease and treatment,” wrote the authors of the study.