Here's one more benefit of exercise: mice who spent their free time on a running wheel were better able to shrink tumors (a 50% reduction in tumor size) compared to their less active counterparts. Researchers found that the surge of adrenaline that comes with a high-intensity workout helped to move cancer-killing immune (NK) cells toward lung, liver, or skin tumors implanted into the mice. The study appears in the journal Cell Metabolism.

Researchers used mice depleted of NK cells to show that the increase in number of NK cells at the site of the tumor was directly contributing to the reduction in size. Even with exercise and a full suite of other immune cells, without the NK cells these mice experienced the normal rate of cancer growth. Blocking the function of adrenaline also blunted the cancer-killing benefits of the running wheel.

The research group also discovered that an immune signaling molecule called IL-6 was the link between adrenaline-dependent mobilization of NK cells and tumor infiltration. It's known that IL-6 is released from muscle tissue during exercise, but authors present evidence that adrenaline specifically hails IL-6 sensitive NK cells and that the IL-6 molecules helped guide the immune cells to the tumors.

While the research is hopeful for patients looking for inexpensive ways to manage their cancer, more needs to be learned about the effects of exercise on metastasis and longevity, as well as if the observations hold true in humans.

http://www.cell.com/cell-metabolism/abstract/S1550-4131(16)30003-1