Over the last decades, the field of exercise medicine has advanced dramatically. It is now widely acknowledged that exercise provides a broad range of health-related benefits for individuals with any type of cancer and at any stage, including improved muscle strength, cardiorespiratory fitness, body composition, chronic inflammation, immune function, pain, fatigue, anxiety and depression. Exercise is also associated with a lower risk of cancer recurrence and mortality, although the biological mechanisms behind this relationship are still not completely understood.
One promising biological explanation involves skeletal muscle. Muscle is not simply a tissue that allows movement; it is an endocrine organ. During contraction, it releases chemicals known as myokines, which enter the bloodstream and influence multiple systems. These molecules contribute to metabolic control, help regulate inflammation, and support immune function. Importantly, several myokines also have the capacity to reduce cancer cell growth and proliferation in laboratory models. However, despite this potential, it remains unclear whether different types of exercise, such as resistance training or high-intensity interval training, could stimulate different myokine responses and if these responses could impact cancer growth and proliferation.
In our recent clinical trial published in January 2026 issue of Medicine & Science in Sports & Exercise®, we investigated this in survivors of breast cancer. Participants completed 3 days per week for twelve weeks of structured and supervised exercise, either resistance training or high-intensity interval training. We observed that systemic myokines increased by up to 15% in both exercise groups. More importantly, the exercise program led to a 22–25% reduction in metastatic breast cancer cells in vitro. This supports the notion that exercise-induced myokines with anti-cancer properties can lower cancer progression.
Interestingly, our results were similar regardless of whether participants completed resistance or high-intensity interval training. We speculate that it was the moderate-to-high intensity and the overall exercise volume that induced the physiological adaptations, rather than the specific exercise modality. Further to this, we also observed meaningful changes in body composition, with participants gaining muscle mass and reducing fat mass after 12 weeks, and these alterations were associated with greater suppression of cancer cell growth. This is important, as our previous work showed that both muscle and adipose tissue release bioactive molecules that can influence cancer development and progression. By altering this balance, exercise may shape the systemic environment in which tumors grow. In simple terms, structured exercise programs create an environment that is less supportive of cancer and this, combined with the release of anti-cancer myokines, may contribute to reduced cancer cell growth.
One of the most encouraging and remarkable aspects is that this occurred in survivors of breast cancer. Although treatments such as chemotherapy and hormone therapy can alter physical and physiological processes, we found survivors of breast cancer still responded to exercise, showing meaningful adaptations. This reinforces an important clinical message that even after cancer treatment, the body can still respond to exercise. It adapts, becomes stronger, and may produce biochemical signals that are less supportive of tumor growth.
These findings matter not only for researchers, but also for clinicians, exercise professionals, and people living with cancer. They highlight the importance of delivering structured exercise programs at sufficient intensity and volume to ensure physical and physiological changes. They suggest that the benefits of exercise extend beyond functional capacity and quality of life, reaching into biological mechanisms that may influence cancer progression. Exercise remains one of the most accessible and empowering tools we have, capable of improving the quality of life of patients with cancer at a low cost for the health system. Integrating exercise medicine into standard care for cancer is imperative, not only to improve how people feel and function, but also to influence the tumor environment in ways that could contribute to a lower risk of cancer recurrence and mortality.
Francesco Bettariga, PhD, is a postdoctoral research fellow at the Exercise Medicine Research Institute at Edith Cowan University in Perth, Australia. Dr. Bettariga has developed a research program investigating how exercise medicine influences tumor biology, with a particular focus on myokines, immune function, and cancer growth. His work aims to translate these findings into practical exercise prescription for patients with cancer. Dr. Bettariga has authored multiple peer-reviewed publications in exercise oncology and is actively involved in integrating exercise into standard cancer care, collaborating with multidisciplinary teams to advance the role of exercise medicine in oncology.
