title: Assessment of intensity, prevalence and duration of everyday activities in Swiss school children: a cross-sectional analysis of accelerometer and diary data.
abstract: BACKGROUND
  Appropriately measuring habitual physical activity (PA) in children is a major challenge. Questionnaires and accelerometers are the most widely used instruments but both have well-known limitations. The aims of this study were to determine activity type/mode and to quantify intensity and duration of children's everyday PA by combining information of a time activity diary with accelerometer measurements and to assess differences by gender and age.
  
  
  METHODS
  School children (n = 189) aged 6/7 years, 9/10 years and 13/14 years wore accelerometers during one week in winter 2004 and one in summer 2005. Simultaneously, they completed a newly developed time-activity diary during 4 days per week recording different activities performed during each 15 min interval. For each specific activity, the mean intensity (accelerometer counts/min), mean duration per day (min/d) and proportion of involved children were calculated using linear regression models.
  
  
  RESULTS
  For the full range of activities, boys accumulated more mean counts/min than girls. Adolescents spent more time in high intensity sports activities than younger children (p < 0.001) but this increase was compensated by a reduction in time spent playing vigorously (p = 0.04). In addition, adolescents spent significantly more time in sedentary activities (p < 0.001) and accumulated less counts/min during these activities than younger children (p = 0.007). Among moderate to vigorous activities, children spent most time with vigorous play (43 min/day) and active transportation (56 min/day).
  
  
  CONCLUSIONS
  The combination of accelerometers and time activity diaries provides insight into age and gender related differences in PA. This information is warranted to efficiently guide and evaluate PA promotion.
authors: Institute of Social and Preventive Medicine, Steinengraben 49, 4051 Basel, Switzerland. bettina.bringolf@unibas.ch.
authors: Bettina
authors: B
authors: Bringolf-Isler
authors: Leticia
authors: L
authors: Grize
authors: Urs
authors: U
authors: Mäder
authors: Nicole
authors: N
authors: Ruch
authors: Felix H
authors: FH
authors: Sennhauser
authors: Charlotte
authors: C
authors: Braun-Fahrländer