Overview

• Edith Cowan University reported that after a 12‑week program, blood drawn at rest from breast cancer survivors reduced in vitro tumor cell growth by about 22% after resistance training and 25% after HIIT.
• The 12‑week trial, published in Medicine & Science in Sports & Exercise, found both modalities raised myokines, with HIIT’s growth‑reduction linked to gains in lean mass and reductions in body fat.
• A separate randomized study of 32 survivors showed a single 45‑minute session of resistance training or HIIT acutely increased circulating myokines and suppressed breast cancer cell growth in vitro.
• HIIT produced the larger immediate rise in IL‑6 and a greater short‑term inhibitory effect on MDA‑MB‑231 cell growth; other tracked myokines included decorin, OSM and SPARC.
• No serious adverse events were reported in the acute bout study, and authors emphasized that these small, lab‑based results do not establish clinical benefit even as broader evidence links exercise to lower recurrence and mortality.