Physical fitness among children with diverse weight status during and after the COVID-19 pandemic: a population-wide, cohort study based on the Slovenian physical fitness surveillance system (SLOfit).

Background: COVID-19 public health crisis has exerted immediate negative impacts on children's physical fitness, but the longer-term effects are not clear, and the impact on children with excess weight is yet unknown. We examined changes in multiple components of physical fitness in response to COVID-19 imposed restrictions, but also a year after the restrictions were terminated, and compared these trends in groups of boys and girls with normal weight, overweight, or obesity before the pandemic. Methods: Information was gathered through Slovenia's national fitness surveillance system, and included 41,330 children (19,890 girls), aged 5-17, who had their fitness levels measured yearly from 2019 to 2022. Multilevel linear mixed models, fitted separately for boys and girls, were used to model the individual-level trends over time in centile score for each fitness test across 3 weight groups. Findings: Overall fitness levels decreased markedly across all weight categories between 2019 and 2020, with the largest decreases in Total Fitness Index observed in children with normal weight and overweight (-8.4 and -7.7 centiles for boys and -8.3 and -8.8 for girls, respectively, p < 0.001). While there was some recovery in the overall fitness level between 2020 and 2022, it remained much lower in 2022 compared to 2019 across most groups, apart from boys with obesity. Fitness components that had the largest impact on general fitness trends were cardiorespiratory fitness, lower body power, body core, and upper body strength. Interpretation: A severe decline in fitness that has not come close to returning to pre-pandemic levels in most population groups of youth begs for urgent population-wide initiatives that will provide additional opportunities for physical activity to youth. Among vulnerable groups, girls with overweight and obesity deserve a special focus of these policies. Funding: Horizon 2020 (Grant no. 774548), Slovenian National Research Agency (Grant no. P5-0142), Croatian Science Foundation (Grant no. DOK-2020-01-3728).

Does time of the day matter? Temporal associations between physical activity and quality and quantity of subsequent sleep in adolescents.

Temporal associations between moderate-to-vigorous physical activity (MVPA) at four different multi-hour intervals during the day and the following indicators of sleep quality and sleep quantity in adolescents were examined. This research is a part of the CRO-PALS study, including 129 adolescents (48 boys, 81 girls; mean age ± SD = 15.6 ± 0.4 years) having complete data on sleep and MVPA measured by the SenseWear Pro3 Armband monitor. As data had a hierarchical structure, repeated measures multilevel modelling was used to assess the associations between PA and sleep. During school nights, in girls, morning MVPA was not related to following indicators of sleep quality and sleep quantity. At the same time, evening MVPA was linked with longer sleep onset latency (ß = 0.064; 95%CI = 0.025 to 0.103) and higher wake after sleep onset (ß = 0.156; 95%CI = 0.0482 to 0.2638). Moreover, during weekend nights, morning MVPA was not associated with sleep, while evening MVPA was accompanied by longer sleep onset latency (ß = 0.058; 95%CI = 0.023 to 0.093), higher wake after sleep onset (ß = 0.104; 95%CI = 0.012 to 0.20), and negatively with sleep efficiency (ß = -0.019; 95%CI = -0.037 to -0.001). In boys the specific multi-hour interval of performing physical activity was not associated with any of indicators of sleep quality. In conclusion, while no strong relations between MVPA and sleep were seen among boys, in girls morning hours MVPA resulted in better sleep patterns over school nights, while afternoon MVPA was followed with slight worsening of some indicators of sleep quality across the whole week.

Accuracy and Precision of Consumer-Grade Wearable Activity Monitors for Assessing Time Spent in Sedentary Behavior in Children and Adolescents: Systematic Review.

BACKGROUND: A large number of wearable activity monitor models are released and used each year by consumers and researchers. As more studies are being carried out on children and adolescents in terms of sedentary behavior (SB) assessment, knowledge about accurate and precise monitoring devices becomes increasingly important. OBJECTIVE: The main aim of this systematic review was to investigate and communicate findings on the accuracy and precision of consumer-grade physical activity monitors in assessing the time spent in SB in children and adolescents. METHODS: Searches of PubMed (MEDLINE), Scopus, SPORTDiscus (full text), ProQuest, Open Access Theses and Dissertations, DART Europe E-theses Portal, and Networked Digital Library of Theses and Dissertations electronic databases were performed. All relevant studies that compared different types of consumer-grade monitors using a comparison method in the assessment of SB, published in European languages from 2015 onward were considered for inclusion. The risk of bias was estimated using Consensus-Based Standards for the Selection of Health Status Measurement Instruments. For enabling comparisons of accuracy measures within the studied outcome domain, measurement accuracy interpretation was based on group mean or percentage error values and 90% CI. Acceptable limits were predefined as -10% to +10% error in controlled and free-living settings. For determining the number of studies with group error percentages that fall within or outside one of the sides from previously defined acceptable limits, two 1-sided tests of equivalence were carried out, and the direction of measurement error was examined. RESULTS: A total of 8 studies complied with the predefined inclusion criteria, and 3 studies provided acceptable data for quantitative analyses. In terms of the presented accuracy comparisons, 14 were subsequently identified, with 6 of these comparisons being acceptable in terms of quantitative analysis. The results of the Cochran Q test indicated that the included studies did not share a common effect size (Q5=82.86; P<.001). I2, which represents the percentage of total variation across studies due to heterogeneity, amounted to 94%. The summary effect size based on the random effects model was not statistically significant (effect size=14.36, SE 12.04, 90% CI -5.45 to 34.17; P=.23). According to the equivalence test results, consumer-grade physical activity monitors did not generate equivalent estimates of SB in relation to the comparison methods. Majority of the studies (3/7, 43%) that reported the mean absolute percentage errors have reported values of <30%. CONCLUSIONS: This is the first study that has attempted to synthesize available evidence on the accuracy and precision of consumer-grade physical activity monitors in measuring SB in children and adolescents. We found very few studies on the accuracy and almost no evidence on the precision of wearable activity monitors. The presented results highlight the large heterogeneity in this area of research. TRIAL REGISTRATION: PROSPERO CRD42021251922; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=251922.