Extension educators have been promoting and incorporating physical activities into their community-based programs and improving the health of individuals, particularly those with limited resources. This article is the first of a three-part series describing the benefits of physical activity for human health: 1) biological health benefits of physical activity, 2) mental health benefits of physical activity, and 3) recommended amounts of physical activity for optimal health. Each part of the series is designed to help Extension educators effectively integrate physical activity into community programs and motivate individuals to maintain an interest in being physically active during and after the program.