We know that children in many parts of the world are spending too much time sitting, often glued to screens. But just how inactive are they? A report in BMJ Open from the Millennium Cohort Study looks at physical activity levels and social, economic and health-related circumstances of nearly 6500 children across the UK. The children wore accelerometers, gadgets that objectively measure movement. Trish Groves, BMJ Open editor in chief, talks to Carol Dezateux, from University College London's Institute of Child Health, about her team's research. Read the full paper here: bit.ly/1fT4Lou