1 Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA 92093, USA; Mary Mackillop Institute for Health Research, Australian Catholic University, Melbourne 3000, Australia. Electronic address: jsallis@health.ucsd.edu.
2 School of Natural and Built Environment, Queen's University Belfast, Belfast BT9 5AG, UK.
3 Department of Physiotherapy, College of Medical Sciences, University of Maiduguri, Maiduguri 600243, Nigeria.
4 Prevention Research Center, Brown School, Washington University in St. Louis, St. Louis, MO 63130, USA.