Muscle–Tumor Crosstalk in Exercise Oncology: Exercise-Induced Myokines and Cancer Cachexia

Exercise-induced myokines, such as IL-6, irisin, and myostatin, play crucial roles in mediating systemic adaptations and modulating tumor progression. This narrative review synthesizes evidence on how regular moderate-intensity exercise affects the myokine network within the tumor microenvironment (TME) of solid tumors. Results from the 86 included studies indicate that structured training (aerobic: 45–65% VO2 max; resistance: 45–70% 1RM) enhances the expression of beneficial myokines that support immune surveillance, reduce inflammation, and improve muscle–tumor cross-talk. IL-6 demonstrates a dual modulatory effect on inflammation and immunity; irisin contributes to tumor apoptosis, while myostatin downregulation supports muscle integrity and metabolic balance. Evidence suggests that exercise-induced alterations in these factors may influence tumor angiogenesis and immune infiltration, offering potential therapeutic implications. Overall, tailored exercise regimens represent a promising non-pharmacological strategy to optimize myokine signaling in cancer management. Further human studies are needed to confirm these mechanistic effects and define optimal exercise protocols. While existing data suggest that structured exercise may beneficially modulate myokine profiles and thereby influence tumor biology, these conclusions are based on limited qualitative evidence rather than quantitative synthesis. Further well-controlled clinical studies are required to confirm causality and define optimal exercise prescriptions for oncology settings.