New research finds exercise—specifically two types—causes the release of elements that may prevent cancer cell growth. New research looks into just that for breast cancer, specifically, and found that high-intensity interval training and resistance training workouts may play a role in stopping cancer cells from returning. The small study, which was published in the journal , analyzed health data from 32 breast cancer survivors. “That may help explain why active people are at lower risk of developing cancer in the first place.”Dr. Grumley agrees. “Even one session produced blood changes that slowed cancer cell growth.