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711. Magnitude and determinants of change in objectively-measured physical activity, sedentary time and sleep duration from ages 15 to 17.5y in UK adolescents: the ROOTS study?

Research Article
Paul J Collings, Katrien Wijndaele, Kirsten Corder, Kate Westgate, Charlotte L Ridgway, Stephen J Sharp, Valerie Dunn, Ian Goodyer, Ulf Ekelund, Soren Brage
May 2015

Commentary: Bethany Walker, GlobalPANet/AusPAnet Executive, National Heart Foundation  

Previous studies have measured adolescent physical activity (PA), sedentary time (ST) and sleep duration (SLP) but have relied on self-reported data. This study aims to provide an accurate picture of PA, ST and SLP through individually calibrated combined heart rate and movement sensors to quantify change. It also examines baseline body composition and activity levels as determinants of change.   

The heart rate and movement sensor was used to estimate PA energy expenditure (PAEE), SLP, ST and time in light (LPA), moderate (MPA), vigorous (VPA), and moderate-to-vigorous physical activity (MVPA). Data was taken from the ROOTS study and examined 144 adolescents (50% boys) aged 15.1 (±0.3)y at baseline and 17.5(±0.3)y at follow-up. Waist circumference (WC), fat mass index (FMI) and fat-free mass index (FFMI) were measured at baseline and follow-up. A mixed-model ANOVA was used to compare baseline and follow-up activity.   

Results indicated PAEE, LPA and ST did not change at follow-up but levels of MPA declined (p ≤ 0.039) for both boys and girls, as did levels of VPA (p = 0.0038) but more for boys than girls. Baseline WC, FMI and FFMI were positively associated with LPA and negatively associated with ST in boys when adjusted for baseline (p ≤ 0.037). From baseline to follow-up SLP increased in both genders (p = 0.004) but was not associated with baseline body composition. Those who recorded high levels of PA also recorded the greatest declines in PA during follow-up.   

High PA intensity declined from mid-to-late adolescence, while the duration of sleep increased. Changes in LPA and ST may be influenced by baseline body composition. As those who engaged in initially high levels of PA also experienced rapid rates of decline it may be best to employ a dual approach; focus efforts on preventing this decline and target those who were consistently inactive to engage in PA. Previous research supports addressing this public health concern particularly considering the evidence indicating childhood behaviours track into adulthood.   

Source: International Journal of Behavioral Nutrition and Physical Activity 2015, 12:6. Access to this article may depend on your institutional right. Click here to access the full article.