Moderate-to-vigorous intensity physical activity among adolescents in the USA during the COVID-19 pandemic

•The study examined adolescents’ physical activity during the COVID-19 pandemic.•Median moderate-to-vigorous physical activity was 2 h per week.•8.9% met physical activity guidelines during the pandemic compared to 16.1% before.•Poor mental health, worry, and stress were associated with lower physical activity.•Higher coping and social support were associated with higher physical activity.