Reactive oxygen species in exercise biology: from adaptive stress response to cell signaling and beyond

• Exercise-induced ROS act as dual regulators of stress and adaptation. • Exercise-induced ROS modulate HSPs and antioxidant components, linking redox fluctuations to proteostasis, cytoprotection, and tissue repair in muscle, blood cells, and metabolic tissues. • Regular physical training reprograms redox homeostasis and establishes a redox “preconditioned” phenotype influenced by age, genetics, and nutritional factors. • Exercise drives multi-organ communication through redox-modulated exerkines and extracellular vesicles (EVs), enabling cross-talk among muscle, cardiovascular, metabolic, and neural tissues.