Background: Only a small proportion of children and adolescents meet current recommendations of at least 60 min of moderate to vigorous physical activity (MVPA) daily. Most of the available data, however, relies on subjective reports; there is limited objective data on physical activity (PA) levels in German primary school children. The purpose of this study, therefore, was to accurately determine how much time children spend undertaking different intensities of PA and being sedentary during weekdays and weekend using objective assessment tools. Gender-specific and age-related differences were examined along with differences between normal weight and overweight/obese children.
Methods: Children's height and weight were measured according to standard procedures and objective PA measurements were determined in a sub-cohort of 384 primary school children (20% of the whole cohort), participating in a large school-based intervention study in south-west Germany (n = 1947). Baseline data collection occurred on six consecutive days, including weekend days, using multi-sensor accelerometry (Actiheart, CamNtech Ltd., Cambridge UK). 318 children (7.1 ± 0.6 years, male: 50%, first grade: 51%) provided data for at least 3 days including one weekend day. According to the amount of energy expended, defined as metabolic equivalents (METs), different activity intensities were categorised as follows: sedentary < 1.5 METs; light = 1.5-3.0 METs; moderate = 3.0-6.0 METs, and vigorous > 6.0 METs.
Results: Average wear time was 1403 ± 94 min/day. Children spent 808 ± 97 min/day being sedentary; 497 ± 72 min/day in light; 128 ± 54 min/day in moderate, and 8 ± 10 min/day in vigorous intensity. 48% of children met the current MVPA guidelines. MVPA was significantly higher on weekdays compared to weekend days (144 ± 66 vs. 113 ± 66 min/day; p < 0.001). Furthermore, boys displayed higher MVPA levels compared to girls (164 ± 57 vs. 106 ± 50 min/day; p < 0.001).
Conclusion: Measured objectively, less than half of primary school children in the study met current PA recommendations, emphasising the necessity for early intervention to promote PA. Consistent with previous research, PA levels were higher in boys and during weekdays. These results indicate that PA levels of girls should especially be promoted in primary schools and that parents should be more involved in interventions to improve PA, particularly during weekends.