1 Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, TX 78712, USA. Electronic address: dsalvo@austin.utexas.edu.
2 Prevention Research Center, Brown School, Washington University in St Louis, St Louis, MO, USA.
3 Centre for Public Health, Queen's University Belfast, Belfast, Northern Ireland, UK.
4 Department of Physical Activity and Healthy Lifestyles, Center for Nutrition and Health Research, National Institute of Public Health, Cuernavaca, Morelos, Mexico.