Protocol for an intergenerational randomized controlled trial to enhance physical activity in older adults at risk for Alzheimer's disease.

Background: Physical inactivity is one of the most important modifiable risk factors for Alzheimer's disease in North America. Despite this, most older adults are physically inactive. It is currently unknown how to successfully motivate physical activity behavior in older adults at risk for Alzheimer's disease, and this knowledge is crucial for early and effective disease prevention.