Until now, systemic biomarkers to measure exercise effects on brain function and that link to relevant metabolic responses were lacking. A study shows a memory biomarker, myokine Cathepsin B (CTSB), increased in older adults following a 26-week structured aerobic exercise training. The positive association between CTSB and cognition, and the substantial modulation of lipid metabolites implicated in dementia, support the beneficial effects of exercise training on brain function and brain health in asymptomatic individuals at risk for Alzheimer's.