Reallocating sedentary time with total physical activity and physical activity bouts in children: Associations with cardiometabolic biomarkers

Time Reallocations From Sedentary Behavior to Physical Activity and Cardiovascular Risk Factors in Children and Adolescents: A Systematic Review

BACKGROUND

Recent statistical approaches have allowed consideration of the integrated relationships between sedentary behavior (SB) and physical activity (PA) with different health outcomes. The present paper aimed to systematically review the literature and synthesize evidence about associations between hypothetical reallocations from SB to different PA intensities and cardiovascular risk factors in youth.

METHODS

A systematic search of 8 databases was performed. Observational studies with a population of children and/or adolescents and based on statistical analysis that investigated the associations between time reallocations from SB to PA and cardiovascular risk factors were included.

RESULTS

Twenty-eight studies met the inclusion criteria. Level of evidence (derived from cross-sectional studies) indicated that the reallocation from SB to moderate to vigorous PA was beneficially associated with adiposity, cardiorespiratory fitness, and cardiometabolic biomarkers in youth. Reallocation from SB to light PA was not associated with the analyzed outcomes. Associations derived from longitudinal studies were mostly inconclusive.

CONCLUSION

Cardiovascular risk factors could be improved by increasing moderate to vigorous PA at the expense of time spent in SB in pediatric populations. Prospective studies or studies investigating the effects of reallocating sedentary bouts to PA are needed.

Transform-Us! cluster RCT: 18-month and 30-month effects on children's physical activity, sedentary time and cardiometabolic risk markers

OBJECTIVE

To test the efficacy of the Transform-Us! school- and home-based intervention on children's physical activity (PA), sedentary behaviour (SB) and cardiometabolic risk factor profiles.

METHODS

A 30-month 2×2 factorial design cluster randomised controlled trial delivered in 20 primary schools (148 Year 3 classes) in Melbourne, Australia (2010-2012), that used pedagogical and environmental strategies to reduce and break up SB, promote PA or a combined approach, compared with usual practice. Primary outcomes (accelerometry data; n=348) were assessed at baseline, 18 and 30 months. Secondary outcomes included body mass index (BMI) and waist circumference (WC) (n=564), blood pressure (BP) (n=537) and biomarkers (minimum n=206). Generalised linear mixed models estimated the interactive effects of the PA and SB interventions on the outcomes. If there was no interaction, the main effects were assessed.

RESULTS

At 18 months, there were intervention effects on children's weekday SB (-27 min, 95% CI: -47.3 to -5.3) for the PA intervention, and on children's average day PA (5.5 min, 95% CI: 0.1 to 10.8) for the SB intervention. At 30 months, there was an intervention effect for children's average day SB (-33.3 min, 95% CI: -50.6 and -16.0) for the SB intervention. Children's BMI (PA and SB groups) and systolic BP (combined group) were lower, and diastolic BP (PA group) was higher. There were positive effects on WC at both time points (SB intervention) and mixed effects on blood parameters.

CONCLUSIONS

The Transform-Us! PA and SB interventions show promise as a pragmatic approach for reducing children's SB and adiposity indicators; but achieving substantial increases in PA remains challenging.

TRIAL REGISTRATION

ISRCTN83725066; ACTRN12609000715279.

Associations between Objectively Determined Physical Activity and Cardiometabolic Health in Adult Women: A Systematic Review and Meta-Analysis

The purpose of this systematic review and meta-analysis was to qualitatively synthesize and quantitatively assess the evidence of the relationship between objectively determined volumes of physical activity (PA) and cardiometabolic health in women. Four databases (PubMed, Web of Science, Scopus, and the Cochrane library) were searched and, finally, 24 eligible studies were included, with a total of 2105 women from eight countries. A correlational meta-analysis shows that moderate-to-vigorous intensity physical activity (MVPA) was favorably associated with high-density lipoprotein (r = 0.16; 95% CI: 0.06, 0.25; p = 0.002); however, there was limited evidence for the effects of most of the other cardiometabolic biomarkers recorded from steps, total physical activity, light- and moderate-intensity physical activity and MVPA. It is most compelling and consistent that being more physically active is beneficial to the metabolic syndrome. Overall, PA levels are low in adult women, suggesting that increasing the total volume of PA is more important than emphasizing the intensity and duration of PA. The findings also indicate that, according to the confounding effects of body composition and cardiorespiratory fitness, meeting the minimal level of 150 min of moderate-intensity physical activity recommended is not enough to obtain a significant improvement in cardiometabolic indicators. Nonetheless, the high heterogeneity between studies inhibits robust conclusions.

Relationship of Physical Activity and Sedentary Time with Metabolic Health in Children and Adolescents Measured by Accelerometer: A Narrative Review

The purpose of this study was to summarize the associations of physical activity (PA) and sedentary time (SED) with metabolic health and examine the effects of time reallocation on metabolic health in adolescents using accelerometer data. A literature search was conducted using PubMed, ScienceDirect, Web of Science, Cochran Library, and Google Scholar, and 27 articles were reviewed. Recent research generally confirms the associations of PA and SED with metabolic health. High PA levels and low SED levels had a positive relationship with metabolic health. Moreover, reallocating 10 min of daily SED to PA was associated with better metabolic health indicators. These results were stronger for moderate-to-vigorous physical activity than for light intensity PA. Thus, efforts to convert SED into PA of at least moderate intensity appear to be an effective strategy to prevent metabolic disease development in children and adolescents. However, some of the associations between PA and metabolic health indicators were inconsistent, depending on age, obesity degree, and PA intensity. Additionally, various accelerometer data collection and processing criteria impact the interpretation of the results. Therefore, consistent accelerometer data collection and analysis methods are needed in future studies. Further, intervention studies are required to verify the causality and effectiveness of the isotemporal substitution model.

Is replacing sedentary time with bouts of physical activity associated with inflammatory biomarkers in children?

This study aimed to investigate the theoretical impact of reallocating a specific amount of sedentary time with an equal amount of (a) total and (b) ≥1-minute bout-accumulated time spent in different activity intensities, on inflammatory biomarkers in 8- to 9-year-old children. Accelerometry and inflammatory biomarker baseline data from the Transform-Us! Study (complete cases n = 149) were utilized. Isotemporal linear models with the Gaussian distribution and identity link functions were used to assess associations between the activity replacements and seven individual inflammatory biomarkers, including C-reactive protein (CRP), and Interleukin (IL)-2, IL-6, IL-8, and IL-10, as well as combined inflammatory and pro-inflammatory composite scores. Eighty-five percent of children met physical activity recommendations. Replacing 10 minutes of sedentary time per day with VPA, regardless of how this was accumulated, was beneficially associated with CRP and both combined composite scores. In contrast, replacing 10 min/day of sedentary time with ≥ 1-minute MPA bouts was detrimentally associated with CRP and the inflammatory composite score. Substitutions with other activity intensities were not significantly associated with any individual inflammatory biomarkers, or combined inflammatory and pro-inflammatory composite scores. In healthy and active school-aged children, evidence of the theoretical impact of replacing sedentary time with physical activity, regardless of intensity or accumulation, on markers of systemic inflammation was limited. Longitudinal research is needed to investigate the long-term impacts of reallocating sedentary time with physical activity, and particularly VPA, for inflammatory biomarkers in children, including those with increased risk of inflammation.

Teachers' Perspective on Strategies to Reduce Sedentary Behavior in Educational Institutions

Standing desks and physical activity breaks can counteract the negative consequences of sedentarism at school. However, the implementation of these strategies should not restrict the pedagogical process. The aim of this study was to assess teachers’ perspectives on strategies to reduce sedentary behavior (SB) of students in the classroom. An online survey was conducted, and the answers were analyzed using descriptive statistics and frequency distribution. The relationships between the variables were assessed using Spearman’s coefficient and a chi-square test. Most teachers believed that a student–furniture mismatch was present. The most common reasons given for not using standing desks were concerns about desks being uncommon and their potential to disrupt the class. However, the majority of the teachers believed it feasible to perform physical activity (PA) breaks during classes. Further intervention studies are needed to determine for which courses the use of standing desks are feasible, for what time periods standing desks should be used, and the appropriate number and layout of standing desks in classrooms.