Physical Activity and Sedentary Time Among U.S. Adolescents Before and During COVID-19: Findings From a Large Cohort Study oleh Ethan T. Hunt, MPH, PhD, Keith Brazendale, PhD, Augusto C.F. De Moraes, PhD, Raja Malkani, MS, Natalia I. Heredia, PhD, Christopher D. Pfledderer, PhD, Denver M. Brown, PhD, Deanna M. Hoelscher, PhD, Michael W. Beets, PhD, Robert G. Weaver, PhD