Eliminating disparities related to physical activity (PA) among low-income and racial/ethnic minority communities (hereinafter referred to as “high-priority groups”) is a complex, dynamic, and multifaceted challenge that requires complex, dynamic, and multifaceted solutions. First, we need to conduct more comprehensive and accurate assessments of PA in order to develop a clearer picture of PA patterns among high-priority groups. To accomplish this goal, self-report assessments of PA should be complemented with more objective and sensitive measures of PA, such as accelerometers, smartphone applications, and wearable technology devices. Self-report assessments also should measure PA across multiple activity domains, including household, transportation, workplace, and recreation/leisure. Sedentary behavior as it relates to PA, weight status, and other health outcomes should be included in these assessments. Furthermore, ecological momentary assessments with repeated and random sampling of PA and sedentary behavior in real time in natural environments should be conducted to minimize recall bias and maximize ecological validity.