Using the R = MC2 heuristic to assess whole-of-school physical activity implementation in elementary schools: a cross-sectional study. - Craig, Derek W.; Lanza, Kevin; Pfledderer, Christopher D.; Pavlovic, Andjelka; Onadeko, Kempson; Heredia, Natalia I.; Injil, Jizyah; DeFina, Laura F.; Walker, Timothy J. (International Journal of Behavioral Nutrition & Physical Activity, 2025)