One session of intense exercise—either resistance training or high-intensity intervals—may help suppress breast cancer cell growth, according to new research from Edith Cowan University.
The study, published in the journal Breast Cancer, found that blood serum taken from breast cancer survivors just after exercising was able to reduce cancer cell growth in lab conditions by up to 30 percent. The effect was traced to muscle-secreted proteins called myokines, which are naturally released during physical exertion and appear to have anti-cancer properties.
Exercise Triggers Anti-Cancer Signals in the Blood
The research team, led by ECU PhD student Francesco Bettariga, recruited 32 women who had completed primary treatment for stage I–III breast cancer. Participants were randomly assigned to complete either a session of resistance training (RT) or high-intensity interval training (HIIT). Blood samples were taken before exercise, immediately after, and 30 minutes later. Those samples were then used to treat triple-negative breast cancer cells in vitro.
- Myokines like IL-6, decorin, SPARC, and OSM rose by 9–47% after exercise
- Cell growth of MDA-MB-231 cancer cells dropped by 20–29% post-exercise
- HIIT produced a greater immediate increase in IL-6 and stronger cell suppression
“The results from the study show that both types of exercise really work to produce these anti-cancer myokines in breast cancer survivors,” said Bettariga. “The results from this study are excellent motivators to add exercise as standard care in the treatment of cancer.”
Not Just Fitness, But Biochemistry
Myokines are hormone-like molecules released by muscles in response to contractions. Scientists have known they help regulate metabolism and inflammation, but this study highlights their direct effect on tumor biology. The researchers observed significant increases in three of the four key myokines studied within minutes of exercise, and reductions in cancer cell proliferation followed quickly.
“Exercise has emerged as a therapeutic intervention in the management of cancer, and a large body of evidence exists that show the safety and effectiveness of exercise as medicine, either during or post cancer treatment,” Bettariga explained.
Importantly, these effects were seen even in survivors whose bodies had been altered by surgery, chemotherapy, or radiation. While HIIT triggered the highest IL-6 response and most rapid tumor suppression, resistance training also significantly elevated myokine levels and reduced cancer cell growth. The findings suggest that even a single workout can launch a physiological cascade that makes the body less hospitable to cancer cells.
Why Body Composition Matters
This single-bout study is part of a broader investigation into how exercise affects inflammation and long-term outcomes in breast cancer survivors. Persistent inflammation is known to contribute to tumor progression and recurrence by inhibiting immune defenses and promoting cell survival and spread.
According to Bettariga, “Strategies are needed to reduce inflammation which may provide a less supportive environment for cancer progression, leading to a lower risk of recurrence and mortality in survivors of breast cancer.”
He added that improving body composition—by increasing muscle and reducing fat mass—appears to be one such strategy. Exercise does both. “If we are able to improve body composition, we have a better chance of decreasing inflammation because we are improving lean mass and reducing fat mass, which is responsible for releasing anti and pro-inflammatory markers,” Bettariga said.
Not a Shortcut: Diet Alone Won’t Do It
Although losing fat mass is part of the equation, Bettariga cautioned against relying on diet alone. “You never want to reduce your weight without exercising, because you need to build or preserve muscle mass and produce these chemicals that you can’t do through just diet alone.”
This nuance is especially important for cancer survivors, who may experience muscle loss due to treatment. Simply shedding pounds without strengthening muscle could inadvertently weaken the very biological defense mechanisms—like myokines—that help reduce recurrence risk.
Looking Ahead: Can One Workout Spark Long-Term Change?
While the anti-cancer effects of a single exercise bout are compelling, researchers are quick to emphasize that more work is needed to understand the long-term benefits. Bettariga and his colleagues hope to follow up with studies tracking how regular training affects cancer recurrence and survival, particularly in relation to inflammation and muscle-derived factors.
Still, for many breast cancer survivors, the message is already clear: your body can fight back—and a single workout may help start that process.
Journal: Breast Cancer
DOI: 10.1007/s10549-025-07772-w
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