Exercise frequency during the COVID-19 pandemic: A longitudinal probability survey of the US population

•First longitudinal study based on population representative sample to examine the effects of COVID-19 mitigation measures on exercise.•Stringent COVID-19 containment measures pose an obstacle for exercise when the overall levels of restrictions were high.•Health inequalities from physical inactivity might exacerbate due to COVID-19.•Safely promoting physical activity to at-risk groups is urgently warranted during the COVID-19 pandemic.