Key Points
- Just one exercise session changed the blood chemistry of breast cancer survivors.
- Levels of muscle-released proteins rose by up to 47% immediately after exercise.
- These proteins slowed breast cancer cell growth in lab tests by up to 29%.
- Both weight training and high-intensity interval training showed the effect.
For years, doctors have said exercise is good for your health. Now a new study shows it may also play a surprising role in fighting cancer, even after just one workout.
Researchers looked at women who had previously been treated for breast cancer. They asked them to complete a single exercise session: either weight training or high-intensity interval training (HIIT), which involves short bursts of effort followed by rest.
Blood was taken before, right after, and 30 minutes after the workout. When the researchers tested that blood in the lab, they found something striking: it slowed the growth of breast cancer cells by up to nearly 30%.
How It Works
The reason appears to be myokines, small proteins that are released by muscles during exercise. These proteins send signals throughout the body and have been linked to healthy metabolism and reduced inflammation.
In this study, several myokines increased by between 9% and 47% immediately after exercise. One of them, called IL-6, stayed elevated even 30 minutes later.
Importantly, when researchers exposed breast cancer cells in the lab to blood taken after exercise, those cells grew more slowly than when exposed to blood taken before exercise.
HIIT vs Weight Training
Both forms of exercise — HIIT and weight training — had a measurable impact. But HIIT led to the biggest immediate rise in IL-6, one of the key proteins.
Still, the researchers said both workouts showed benefits, reducing cancer cell growth by roughly 20–29% compared to baseline.
Why This Matters
Breast cancer is the most common cancer in women. While many treatments exist, survivors still face the risk of the disease returning.
The study’s authors believe these results provide a potential explanation for why exercise has been linked to better survival outcomes in people with cancer.
They wrote:
“A single bout of resistance training or HIIT can increase levels of anti-cancer myokines and reduce the growth of cancer cells in vitro, potentially contributing to a lower risk of recurrence.”
Francesco Bettariga, the lead researcher and a PhD student at Edith Cowan University in Australia, explained that the study shows how exercise can have anti-cancer effects at the cellular level.
This, he said, may help explain why physical activity is linked to lower risks of cancer coming back, spreading, or leading to death. He added that while the study has limitations and more research in living patients is still needed, the results highlight how exercise could play a role in improving survival for people with cancer.
What’s Next
A single bout of exercise in breast cancer survivors caused temporary increases in muscle‑released proteins (myokines), and plasma taken after exercise slowed breast cancer cell growth in laboratory tests by up to 29%.
While the findings provide a possible biological explanation for exercise’s long‑term benefits, the study does not prove that one workout directly reduces cancer recurrence or progression in patients.
The research was done in the lab, using blood samples tested against cancer cells. The study did not track whether these changes directly prevent cancer from coming back in real life.
The team noted that larger and longer studies are needed especially to see how regular workouts, not just a single session, may affect cancer growth and recurrence over time.
For now, the results add to a growing body of evidence that exercise does more than improve fitness. It could also play a role inside the body’s fight against one of the deadliest diseases.
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Source: Bettariga, F., Taaffe, D.R., Crespo-Garcia, C., Clay, T.D., De Santi, M., Baldelli, G., Adhikari, S., Gray, E.S., Galvão, D.A. and Newton, R.U., 2025. A single bout of resistance or high-intensity interval training increases anti-cancer myokines and suppresses cancer cell growth in vitro in survivors of breast cancer. Breast Cancer Research and Treatment, 213(1), pp.171–180
