Randomized trials of various exercise interventions have proven that exercise has many systemic benefits. Data are emerging that physical activity may improve cognition - specifically executive function - in healthy adults. The researchers' own pilot data suggest that resistance training in seniors may improve executive functioning as assessed by neuropsychological tests and neuro-imaging. However, at present the Cochrane Database of Systematic Reviews indicates there are insufficient published data to guide exercise prescription to prevent AD. In persons with MCI, no published studies have reported on whether physical activity can improve executive function, or delay its decline and thus, prevent or delay the onset of functional dependence (and later, dementia).