Despite rapid growth in resources devoted to physical activity promotion, the public health capacity to address physical inactivity is insufficient. Too few public health practitioners have the necessary skills to implement and evaluate evidence-based physical activity interventions, and schools of public health typically do not have adequate course content in physical activity. This commentary discusses the types of initiatives needed to improve the education and training of physical activity practitioners and researchers to effectively address one of the 21st century's greatest health problems—an inactive lifestyle.