Association between objectively evaluated physical activity and sedentary behavior and screen time in primary school children

Tanaka et al. BMC Res Notes (2017) 10:175 DOI 10.1186/s13104-017-2495-y BMC Research Notes RESEARCH ARTICLE Open Access Association between objectively evaluated physical activity and sedentary behavior and screen time in primary school children Chiaki Tanaka1*, Maki Tanaka2, Masayuki Okuda3, Shigeru Inoue4, Tomoko Aoyama5 and Shigeho Tanaka5 Abstract Background: Even when meeting guidelines for physical activity (PA), considerable sedentary time may be included. This study in primary school children investigated the relationships between objectively evaluated sedentary and PA times at different intensities using triaxial accelerometry that discriminated between ambulatory and non-ambulatory PA. The relationships between subjectively evaluated screen time (i.e. time spent viewing television and videos, playing electronic games, and using personal computers) and objectively evaluated sedentary and PA times were examined. Methods: Objectively evaluated sedentary and PA times were assessed for 7 consecutive days using a triaxial accelerometer (Active style Pro: HJA-350IT) in 426 first to sixth grade girls and boys. Metabolic equivalents [METs] were used to categorize the minutes of sedentary time (≤1.5 METs), light PA (LPA, 1.6–2.9 METs), moderate-to-vigorous PA (MVPA, ≥3.0 METs) and vigorous PA (VPA, ≥6.0 METs). The physical activity level (PAL) was calculated using the mean MET value. Subjectively evaluated screen time behaviors were self-reported by participants and parents acting together. The associations between PA and sedentary and screen time variables were examined using partial correlation analyses. Results: After adjustment for age, body weight and wearing time, objectively evaluated sedentary time correlated strongly with non-ambulatory and total LPA and PAL, moderately with ambulatory LPA, non-ambulatory or total MVPA, and weakly with ambulatory MVPA, ambulatory, non-ambulatory or total VPA. Subjectively evaluated screen time was not associated significantly with objectively evaluated sedentary and PA times or PAL. On average, each reduction of 30 min in daily sedentary time was associated with 6 or 23 min more of MVPA or LPA, respectively. Conclusions: These findings show that higher daily sedentary time may be compensated mainly by lower LPA, while the association between sedentary time and MVPA was moderate. Therefore, improving MVPA and reducing sedentary time are important in primary school children. Keywords: Exercise, Ambulatory activity, Non-ambulatory activity, Sitting, Accelerometer, Screen time Background The World Health Organization guidelines on physical activity (PA) recommend at least 60 min every day of *Correspondence: c‑ 1 Division of Integrated Sciences, J. F. Oberlin University, 3758 Tokiwamachi, Machida, Tokyo 194‑0294, Japan Full list of author information is available at the end of the article moderate-to-vigorous physical activity (MVPA) in order to benefit the health of children and adolescents [1]. However, considerable sedentary time can be accumulated even when these PA guidelines are met. For example, Marshall et al. [2] reported that clusters of UK and USA adolescents of both genders had higher than average levels of PA, but also increased levels of screen-based sedentary behavior or sedentary socializing activities. © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Tanaka et al. BMC Res Notes (2017) 10:175 Sedentary behavior is usually defined as behaviors carried out in a seated or reclining position with an energy cost of ≤1.5 METs [3]. A previous systematic review of the relationship between sedentary time or sedentary behavior and health-related outcomes in children and adolescences showed that long periods of sedentary activity were associated with adverse health outcomes [4–7]. Recently, guidelines for sedentary behavior in children and adolescents have been published in several countries [8–10]. Whether or not more time spent in MVPA is associated with higher physical activity level (PAL) remains an interesting question. One of the first studies to examine this possibility was carried out in adults [11]. A multiple regression analysis of the proportion of time spent on moderate or high intensity activities showed that only moderate intensity activity was a significant predictor of PAL (r2 = 0.51), while the proportions of low and moderate intensity activities influenced total energy expenditure. Recently, Pearson et al. [12] reviewed several observational studies that examined the association between PA and sedentary behavior or sedentary time in young people (<18 years), and showed only a weak negative association. However, only a small number of studies have examined the associations between objectively evaluated PA and sedentary time [13]. Previous studies proposed using prediction models of metabolic equivalents (METs) for children with accelerometers. The slope and intercept of ambulatory activities in a predictive model such as walking and running are different from those of non-ambulatory activities, like playing games, cleaning, playing with blocks, tossing a ball, and aerobic dance [14–17]. Based on the variability in accelerometer counts, Hikihara et al. [18] showed a discrimination between ambulatory activities, such as continuous walking or jogging and non-ambulatory activities, including lifestyle activity. Our previous study in primary school children reported that ambulatory light PA (LPA) and MVPA and non-ambulatory LPA were lower in the summer vacation than during the school year in both genders [19]. We also observed that nonambulatory MVPA in girls was significantly lower during the summer vacation than in the school year. Another study in preschool children showed that 25 m run speed, skill-related physical fitness total Z-score, and total physical fitness Z-score (health-related and skill-related physical fitness total Z-score) correlated positively with the time spent in ambulatory activity [20]. Moreover, thin preschool children spent significantly less time engaged in ambulatory PA than normal-weight or overweight children [21]. Although the contribution of ambulatory and non-ambulatory PAs to health outcomes in children has not been well established [20, 21], physical fitness Page 2 of 8 and weight status in children correlated to the types of PA, MVPA was shown to make up approximately 40–45% of non-ambulatory activity in primary school boys and (...truncated)