Ageing is a scientifically fascinating and complex biological occurrence characterised by morphological and functional changes due to accumulated molecular and cellular damage impairing tissue and organ function. Ageing is often accompanied by cognitive decline but is also the biggest known risk factor for Alzheimer’s disease, the most common form of dementia. Emerging evidence suggests that sedentary and unhealthy lifestyles accelerate brain ageing, while regular physical activity, high cardiorespiratory fitness (CRF), or a combination of both, can mitigate cognitive impairment and reduce dementia risk.