Abstract
BackgroundLow levels of physical activity and high time spent in sedentary activities have been associated with unfavourable health outcomes in adolescents. During adolescence, physical activity declines and sedentary time increases, however little is known about whether the magnitude of these changes differs within or between school-time, after-school time, or at weekends.MethodsAdolescents (n = 363) participating in the PEACH (Personal and Environmental Associations with Children’s Health) project provided accelerometer data at 12 and 15 years of age. Data were collected in 2008/2009 and 2012/2013. Time spent sedentary (<100 cpm), in light physical activity (LPA (100-2295 cpm) and in moderate to vigorous physical activity (MVPA: ≥ 2296 cpm) were generated for school-time, after-school time and for weekends using school-specific start and finish times. All data were analysed in 2014.ResultsThe proportion of time spent sedentary significantly increased during school (+8.23%, 95% CI = 7.35 to 9.13), after-school (+6.99%, 95% CI = 5.91 to 8.07) and at weekends (+6.86%, 95% CI = 5.10 to 8.62). A parallel decrease was found in the proportion of time spent in LPA during school (-7.62%, 95% CI = -8.26 to -6.98), after-school (-7.01%, 95% CI = -7.74 to -6.28) and at weekends (-6.72%, 95% CI = -7.80 to -5.65). The proportion of time spent in MVPA remained relatively stable during school (-0.64, 95% CI = -1.11 to -0.18), after-school (0.04%, 95% CI = -0.58 to 0.67) and at weekends (-0.14%, 95% CI = -1.18 to 0.90).ConclusionsObjectively measured sedentary time increased between 12 and 15 years of age during-school, after-school, and at weekends, suggesting that interventions aiming to reduce the age-associated changes in sedentary time are needed in all three time contexts. Future work should identify which sedentary activities change more than others to inform interventions which aim to minimise the increase in time spent sedentary during adolescence.
Highlights
Low levels of physical activity and high time spent in sedentary activities have been associated with unfavourable health outcomes in adolescents
Low physical activity (PA) in youth is associated with a range of adverse health outcomes [1,2] relatively few adolescents meet physical activity guidelines [3,4] In addition, there is emerging evidence that sedentary behaviours in adolescence are negatively associated with adolescent health outcomes such as obesity and metabolic risk [5,6,7] the evidence for this using objective measures are inconsistent [8,9,10]
The results showed that children were more active on weekdays compared with weekend days
Summary
Low levels of physical activity and high time spent in sedentary activities have been associated with unfavourable health outcomes in adolescents. Brooke et al [19] systematically reviewed and metaanalysed the literature on time specific differences in objectively measured physical activity in school children aged 4-18 years They compared total physical activity and MVPA between time segments (weekday vs weekend day, in school vs out of school, weekend vs out of school and lessons vs break times). The authors suggest that this is because schools have opportunities to engage in higher intensity physical activity such as during PE lessons, there is the inherent requirement to be sedentary for a large portion of school time [19] These data were not presented as a proportion of time and due to the different time frames these are not directly comparable. It is worth noting that they did not investigate age differences and as the demands of school increase with age it is expected that these patterns would differ by age
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