Why have youth physical activity trends flatlined in the last decade? Opinion piece on “Global trends in insufficient physical activity among adolescents: a pooled analysis of 298 population-based surveys with 1.6 million participants” by Guthold et al.

• Globally, physical inactivity rates in school-going adolescents are alarming. Using realist and co-creation methodologies to better understand and develop multisectoral strategies and programs and efforts to promote effective uptake of evidence-based programs into routine practice at scale are urgently...