41. Why does exercise help even though it is a stress?

Exercise is a controlled stress that triggers adaptive remodeling: improved mitochondrial function, vascularization, proteostasis, immune regulation, and metabolic flexibility. From the deleteriome perspective, exercise may transiently increase certain stress markers while decreasing long-term burden by strengthening maintenance capacity and increasing functional reserve. This illustrates a general point: the direction of short-term biomarker change is not always the direction of long-term risk change; context and timescale matter. The goal is not to avoid all stress, but to engage stresses that train defenses and improve recovery.