Single Session of Resistance or HIIT Raises Myokines and Slows Breast Cancer Cells in Lab Tests, Study Finds

A single 45-minute session of resistance training or high-intensity interval training (HIIT) raised levels of muscle-derived proteins known as myokines in the blood of breast cancer survivors and reduced the growth of breast cancer cells in laboratory tests by an estimated 20 to 30 percent, researchers in Australia reported.

The study enrolled 32 women who had completed treatment for stage I to stage III breast cancer at least four months earlier. Participants, whose average age was 59 and whose mean body mass index was 28, were randomly assigned to perform a one-time bout of either resistance exercise or HIIT. Blood samples were taken before exercise, immediately after exercise and 30 minutes later to measure circulating myokines, which are proteins released by skeletal muscle during exercise and are known to influence metabolism and inflammation.

In the resistance group, participants completed five sets of eight repetitions targeting major muscle groups, including chest press, seated row, shoulder press, lateral pulldown, leg press, leg extension, leg curl and lunges, with one to two minutes of rest between sets. The HIIT group performed seven 30-second all-out efforts on equipment such as a stationary bike, treadmill, rower or cross-trainer, with three-minute recovery intervals. Both protocols lasted about 45 minutes in total.

Researchers reported immediate rises in several myokines after a single session. Interleukin-6 (IL-6) increased by as much as 47 percent immediately after HIIT. In the resistance group, decorin rose by 23 percent and IL-6 by about 9 percent. Myokine levels began to fall after exercise but remained above baseline during the short follow-up window.

Using participants' post-exercise blood serum in laboratory assays, the team observed reductions in the proliferation of breast cancer cells, estimating a 20 to 30 percent slowdown in growth compared with baseline serum. "By demonstrating anti-cancer effects at the cellular level, our results provide a potential explanation for why exercise reduces the risk of cancer progression, recurrence, and mortality," Francesco Bettariga, lead study researcher and a PhD student at Edith Cowan University, said in a statement.

The researchers published their findings this summer in the journal Breast Cancer Research and Treatment. They noted that both resistance training and HIIT produced comparable anti-cancer effects in their laboratory tests, suggesting that exercise intensity rather than exercise modality may drive the acute release of cancer-suppressive myokines.

Myokines can interact with immune pathways and suppress inflammatory molecules called cytokines; chronic inflammation is a recognized contributor to DNA damage and cancer development. The study linked the acute rise in myokines to potential suppression of inflammatory signaling and slower cancer cell growth in vitro, but the authors cautioned that these laboratory findings do not by themselves prove a clinical benefit in patients.

Experts not involved with the study said the results add to a growing body of evidence that exercise has biologic effects relevant to cancer outcomes but emphasized the preliminary nature of the data. The study's limitations include its small sample size, the focus on a single cancer type, and measurement of immediate, short-term changes after one exercise session. The observed reductions in cancer cell growth were measured in vitro using participants' serum rather than directly in patients.

Breast cancer remains one of the most common cancers among women in the United States, with about 311,000 new cases and 42,000 deaths annually, according to the American Cancer Society. Incidence has risen modestly over recent decades; a study in JAMA reported an approximate 0.8 percent annual increase in breast cancer incidence from 2000 to 2019.

Bettariga and colleagues said further research is needed to examine whether repeated, long-term exercise programs can produce sustained anti-cancer responses in vivo, to test effects in other cancer types and to clarify the role of immune mechanisms. "While our study has limitations and further in vivo work is needed, these findings highlight how exercise could contribute to improved survival outcomes in people with cancer," Bettariga said.

Until larger clinical trials are completed, clinicians and patients may consider this evidence alongside existing recommendations that regular physical activity reduces the risk of chronic disease and improves overall health. The study adds a mechanistic link at the cellular level between acute exercise and processes that could influence cancer progression, but it does not yet establish that a single workout will change clinical outcomes for people with cancer.