Physical Activity, Inactivity, and Health During Youth.

2016 has been an exciting year for research in physical activity, inactivity and health. Recognition of the importance of all physical behaviours (physical activity, sedentary time and sleep) across the 24 h day continues to grow. Notable advances have included: applications of recent methodological innovations that account for the co-dependence of the behaviours in the finite 24 h period showing that the balance of these behaviours is associated with health; methodological innovations focussing on the classification of behaviours and/or quantification of the 24 h diurnal activity pattern; and a series of systematic reviews that helped provide the evidence base for the release of the innovative 24 h movement guidelines earlier this year. This commentary focuses on just two of these papers: the first by Goldsmith and colleagues who demonstrate a new statistical method that exploits the time series nature of accelerometer data facilitating new insights into time-specific determinants of children’s activity patterns and associations with health; the second by Tremblay and colleagues who describe the evidence base for associations between each physical behaviour and children’s health, the emerging evidence base for associations between the balance of behaviours and health, and development of the world’s first 24 h movement guidelines. Novel insights into activity patterns in children, found using functional data analyses Goldsmith J, Liu X, Jacobson J, Rundle A.