The current study provides for the first time up-to-date information on objectively assessed sedentary time and different PA intensities among representative samples of 10- to 12-year-old children across five countries in Europe. The results show that very few boys and girls across Europe met the recommendations of 60 minutes MVPA per day and that they spent approximately eight hours per day being sedentary. Boys did somewhat better than girls, and rather large differences between countries were observed. The results strongly confirm that obesity prevention programs focusing on promoting PA and reducing sedentary time in this age group are needed and such efforts should be further intensified. Although evidence-based recommendations for maximum levels of sedentary time do not exist, eight hours per day certainly appears to be a bit too much sitting, especially for young people. Thus, interventions focusing particularly on reducing sitting time, next to promoting PA, should be considered. As it may not be feasible to replace a lot of time spent sedentary by MVPA, it could be advisable to promote LPA as an alternative to sedentary pursuits . For adults, replacing sedentary activities by PA of light intensity, such as standing and walking around, appeared to be a practicable strategy . For children, there is the added evidence that LPA contributes to total daily energy expenditure, resulting in beneficial associations with blood glucose and overweight [16, 34]. A recent study of Janz et al.  showed that LPA may have a beneficial effect against excess adiposity in older children. Nevertheless, future research should further investigate whether replacing sedentary activities by LPA could have an impact on children's health. Furthermore, since the predominant activity at school is sitting in class , more innovative intervention strategies may be considered such as breaking up sedentary time between lessons and changing the school or class environment .
Regarding the time spent in MVPA, the mean level among European children was far below recommendations. Only 4.6% of the European girls and 16.8% of the European boys reached the recommended 60 minutes MVPA per day. These percentages are alarming and imply an urgent need to develop effective PA promotion programs. Riddoch et al.  found that almost all 9-year-old children across four European countries fulfilled MVPA recommendations. However, different cut-points were used in that study (> 906 cpm equals moderate activity), classifying activities with a lower intensity value already as 'moderate' intensity. More severe cut-points were used in the present study  which makes it impossible to compare results between the two cross-European studies.
Comparable to previous studies [37–39], the current study established gender differences in both sedentary time and PA across all countries. Girls spent more time being sedentary and less time in all PA intensities than boys. These gender differences in the transition from childhood to adolescence are the precursors of the larger gender differences in adolescence . Intervention programmes to promote PA and to reduce sedentary time should therefore merit special attention to girls. For example, the NEAT girls intervention has recently developed a specific programme to promote PA among girls with lifestyle physical activities and appealing school sport sessions (e.g. yoga, Pilates, skipping choreography) . However, we are not aware of intervention programmes to reduce sedentary time among girls specifically. Future research should further investigate the specific reasons of the differences in PA and sedentary time among girls and boys.
Furthermore, the current study disclosed some cross-European differences in the levels of sedentary time and PA, possibly due to political and environmental differences. In general, Greek children spent more time sedentary in comparison to the other children and Swiss children spent more minutes in MVPA in comparison to the other children. Especially for Swiss children, there is a large difference in MVPA with the other European countries. A possible explanation for differences between countries is the different organization of PA and sports (e.g. financial issues and spending priorities in the field of sport). The Swiss national sports policy for example considers 'health' as the first priority with more physically active people as the main objective . There is also a national sports programme 'Youth and Sport' which offers optional physical education lessons after school . However, not all differences are situated on country-level, since PA facilities and opportunities differ between schools as well. Physical education can be considered to have a major influence on children's PA time , e.g. Hungarian and Swiss schools provide three hours of physical education per week, whereas Belgian, Greek and Dutch schools provide two hours per week. In brief, schools play a major role in PA promotion. To our knowledge, there are no policy measures in the European countries with regard to sedentary time. However, political institutions should be made aware of the importance of the time children spent sedentary and should definitely pay attention to this topic in the future . Despite some country differences, obesity prevention programmes focusing on sedentary time and PA are clearly needed in all European countries. Time spent sedentary was namely high in every country and the mean amount of minutes MVPA was below the recommended 60 minutes for almost all children.
The most important strengths of the current study were the specific focus on sedentary time and LPA, the relatively large sample of children across several European countries, the use of accelerometry to objectively assess different levels of PA and sedentary time and the use of a standard protocol for data collection and data processing. However, when using accelerometers, there are some limitations as well: accelerometers do not measure arm movement or swimming activities, do not distinguish between lying, sitting and standing still and underestimate the intensity of cycling and some other activities. A second limitation of the current study is the relatively large drop-out of accelerometer-data due to insufficient valid days. It is possible that the children who dropped out were less physically active and not interested in wearing an accelerometer or conversely, were more active and experienced the accelerometer as an inconvenience during exercise. A final possible limitation is the use of three different models of Actigraph accelerometers (GT1M, GT3X and Actitrainer). Since two triaxial and one uniaxial accelerometer model was used, we only made use of the vertical axis output for the present study. The Actitrainer and the GT3X have identical triaxial accelerometers and a recent study showed that the vertical axis output for the GT3X is similar as for the GT1M . However, it has also been posited that the reduced sensitivity in low-count ranges in the GT1M may make it somewhat less suited for monitoring sedentary time and LPA .