BackgroundPhysical activity and sedentary behaviour in youth have been reported to vary by sex, age, weight status and country. However, supporting data are often self-reported and/or do not encompass a wide range of ages or geographical locations. This study aimed to describe objectively-measured physical activity and sedentary time patterns in youth.MethodsThe International Children’s Accelerometry Database (ICAD) consists of ActiGraph accelerometer data from 20 studies in ten countries, processed using common data reduction procedures. Analyses were conducted on 27,637 participants (2.8–18.4 years) who provided at least three days of valid accelerometer data. Linear regression was used to examine associations between age, sex, weight status, country and physical activity outcomes.ResultsBoys were less sedentary and more active than girls at all ages. After 5 years of age there was an average cross-sectional decrease of 4.2 % in total physical activity with each additional year of age, due mainly to lower levels of light-intensity physical activity and greater time spent sedentary. Physical activity did not differ by weight status in the youngest children, but from age seven onwards, overweight/obese participants were less active than their normal weight counterparts. Physical activity varied between samples from different countries, with a 15–20 % difference between the highest and lowest countries at age 9–10 and a 26–28 % difference at age 12–13.ConclusionsPhysical activity differed between samples from different countries, but the associations between demographic characteristics and physical activity were consistently observed. Further research is needed to explore environmental and sociocultural explanations for these differences.Electronic supplementary materialThe online version of this article (doi:10.1186/s12966-015-0274-5) contains supplementary material, which is available to authorized users.

No abstract

The GENEA is a reliable and valid measurement tool capable of classifying the intensity of physical activity in adults.

Despite widespread use of accelerometers to objectively monitor physical activity among adults and youth, little attention has been given to older populations. The purpose of this study was to define an accelerometer count cutpoint for a group of older adults and to then assess the group's physical activity for 7 days. Participants (N=38; 69.7 ± 3.5 years) completed a laboratory-based calibration with an Actigraph 7164 accelerometer. The cutpoint defining moderate to vigorous physical activity (MVPA) was 1041 counts per minute. On average, participants obtained 68 minutes of MVPA per day, although more than 65% occurred as sporadic activity. Longer bouts of activity occurred in the morning (06:00-12:00) more frequently than other portions of the day. Almost 14 hours per day were spent in light intensity activity. This study demonstrates the rich information accelerometers provide about older adult activity patterns-information that may further our understanding of the relationship between physical activity and healthy aging.