Could a simple workout session make a difference for breast cancer survivors? Recent research from Edith Cowan University, published in Breast Cancer Research, suggests it just might.

Scientists explored the effects of two popular exercise routines—resistance training and high-intensity interval training—on the body’s natural ability to suppress breast cancer cell growth. The results are not only intriguing but also bring fresh hope for those seeking ways to lower their risk of cancer coming back.

Let’s set the scene. Breast cancer is a global challenge. Every year, millions of women hear the diagnosis. In 2022, 2.3 million new cases were recorded worldwide. It remains the most common cancer and the leading cause of cancer-related deaths among women. Breast cancer rates in Malaysia are rising. In 2016 report, the age-standardized incidence rate stood at 34.1 per 100,000 women—an increase from previous years. More worrying is the early onset of the disease: 13.6% of women diagnosed are under 40, a stark contrast to just 5% in Western countries.

Although treatment advances have improved survival, recurrence is still a real concern. Depending on several factors, including tumour type and treatment received, between ten and thirty per cent of survivors may face cancer returning years later.

Against this background, exercise has been gaining attention. No longer just a tool for general fitness, it is now seen as “medicine” for those with cancer. International guidelines recommend it for patients and survivors alike. Exercise relieves fatigue, improves quality of life, and can even help manage weight. What’s more, being active has been linked to a reduced risk of breast cancer returning, as well as lower mortality rates. But how does exercise achieve these benefits? This is where the story gets fascinating.

A growing body of evidence points to the role of myokines. These are proteins released by muscles during and after exercise. You can think of them as messages sent out by your muscles—chemical signals that travel through the bloodstream. Researchers have known that myokines can influence organs like the heart, brain, and liver. Now, their potential anti-cancer properties are under the microscope.

Key examples include interleukin-6 (IL-6), decorin, oncostatin M (OSM), and SPARC. Laboratory studies suggest that these myokines can slow or even halt the growth of certain cancer cells. IL-6 may trigger cancer cell death and block their multiplication. OSM appears to keep cancer cells dormant. Decorin interferes with tumour growth by changing the environment around tumours, while SPARC affects how cancer cells stick together and move.

But most previous research has involved healthy people or animal models, not actual breast cancer survivors. That is a crucial gap. Cancer and its treatments can change how the body responds to exercise at a biological level. It was time to see what really happens in those who have lived through treatment.

The new study recruited 32 women who had completed their primary breast cancer treatment at least four months earlier. They were randomly split into two groups: one performed resistance training, focusing on weights and muscle strength; the other did high-intensity interval training, mixing short bursts of vigorous cardio with brief recovery periods.

Each participant gave blood samples before exercise, immediately after, and again half an hour later. These samples were analysed for levels of the key myokines mentioned earlier. But the researchers did not stop there. They also used the blood serum to “feed” an aggressive type of breast cancer cell (known as MDA-MB-231) in laboratory dishes, tracking how fast these cells grew in response.

What did they find? Both forms of exercise led to noticeable spikes in the levels of several myokines straight after the session. IL-6 shot up—much higher in those who did interval training than in those who lifted weights. Decorin and SPARC also increased in both groups post-exercise. OSM went up significantly after resistance training but not as much after interval training.

Perhaps more importantly, when scientists put the post-exercise serum onto breast cancer cells in the lab, they saw something remarkable. The cancer cells grew much more slowly—by about twenty per cent less—compared to those exposed to blood collected before exercise. This effect was particularly strong immediately after the workout and persisted at least thirty minutes later. High-intensity interval training serum showed an even greater effect than resistance training at suppressing cell growth right after exercise.

Why does this matter? For one thing, it provides direct evidence that something in the blood after exercise—likely these myokines—can disrupt the growth of aggressive cancer cells outside the body. While this does not prove that a single workout will stop cancer in its tracks within the body, it adds weight to the argument that regular physical activity could help keep recurrence at bay.

It’s also worth noting that these findings apply to triple-negative breast cancer cells. This type is especially tough to treat since it does not respond to hormone therapies. The possibility that exercise-induced changes in blood chemistry could slow their growth opens new avenues for non-drug interventions.

There are practical implications too. Exercise is accessible, low-cost, and rarely causes serious side effects compared to many medical treatments. For survivors who may feel anxious about recurrence or overwhelmed by ongoing medication regimens, knowing that a brisk walk or a session with weights could activate such powerful biological defences is empowering.

However, as promising as these results sound, there are caveats. The study only looked at one type of breast cancer cell in vitro—that is, outside the body in controlled lab conditions. The human body is far more complex than any petri dish. Blood flow, immune system activity, and other factors play a role in real-life tumour suppression that cannot be captured here.

Additionally, only a select group of myokines was measured. There may be other molecules or pathways involved that scientists have yet to uncover. The researchers also did not collect detailed information on medications taken by participants, which could have influenced results.

Despite these limitations, experts believe this is an important step forward. It is one of the first randomised studies to compare different types of exercise head-to-head in survivors rather than healthy volunteers or patients still undergoing treatment.

So what should breast cancer survivors take away from all this? Firstly, both resistance training and interval-style cardio offer benefits—not just for fitness or mental wellbeing but potentially for reducing cancer risk at a molecular level too. While HIIT appeared to give a slightly bigger boost to IL-6, both routines led to meaningful increases in anti-cancer myokines and suppressed cell proliferation.

Secondly, these benefits happened after just one session. Imagine what could happen with regular workouts over weeks and months! Of course, no one should expect miracles overnight or view exercise as a replacement for prescribed medical care. But adding moderate to vigorous physical activity into weekly routines could be an extra layer of defence—one that is firmly within reach.

Looking ahead, researchers say longer-term studies are needed. They plan to explore whether repeated bouts of exercise continue to produce these positive changes and if they translate into fewer recurrences over time. There is also interest in using more advanced models that mimic real tumours more closely and examining how factors like baseline fitness or ongoing medications affect results.

For now, this research offers both reassurance and motivation for anyone navigating life after breast cancer. The message is simple: movement matters—not just for heart health or mood but as an active ally in keeping cancer at bay.

Scientists at Edith Cowan University have provided fresh evidence that physical activity—whether lifting weights or tackling intervals—can spark biochemical changes with the potential to slow breast cancer cell growth. Their findings support current guidelines encouraging all survivors to stay active for better health outcomes.

So next time you think about skipping that gym session or brisk walk outdoors, remember: your muscles might be doing more than you think—not only making you stronger but also sending out messages that help protect your future.