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30th Apr 2024

Light has an impact on human sleep and circadian rhythm. Morning sunlight has an important role in adjusting the human circadian rhythm to 24 hours, but exposure to artificial light at night can be a cause of the delay of the circadian rhythm and sleep timing. Our previous studies showed that the effects of light at night are greater in children than adults. In the present study, we examined if the individual difference in sleep timing and circadian phase in children is related to the magnitude of melatonin suppression by light at night, an index of circadian sensitivity to light at night. Twenty-one healthy children aged 9 to 14 participated in this experiment. Informed consent was obtained from all participants and their parents. The participants were asked to record a sleep diary two weeks before the experiment. Saliva samples were collected to measure melatonin concentrations every hour from 17:00 to the habitual bedtime under ordinary room light conditions (200 ± 30 lx) on the first day and under dim light conditions (<30 lx) on the second day. Dim light melatonin Onset (DLMO) was used as an index of the circadian phase, and the percentage of melatonin suppression by light was calculated as an index of circadian sensitivity to light. Individual difference in the percentage of melatonin suppression was correlated with DLMO (r=0.535, p=0.039) and habitual sleep onset time (r=0.503, p=0.056). The children sensitive to light showed delayed circadian phase and sleep onset time. This result suggests that individual differences in circadian sensitivity to light before bedtime influence circadian rhythm and sleep in children.

Introduction: Adherence to the 24-hour movement behaviors (24-HMB) guidelines has been positively associated with health indicators in adolescents. However, evidence regarding changes in the proportion of adolescents meeting these guidelines over time is scarce. This study aimed to determine changes in the proportion of adherence with 24-HMB recommendations during adolescence. Methods: Prospective study (with mean follow-up period of 3.2 years) comprising 117 adolescents (53.8% girls) from public school in the southern region of Brazil. Physical activity (PA) was objectively measured, while sedentary behavior (SB) and sleep were estimated using a self-administered instrument. The 24-HMB were dichotomized in adherence or non-adherence, according to international recommendations: i) moderate to vigorous physical activity ≥60 min/day; ii) sedentary behavior ≤2 hours/day of recreational screen time (TV); and iii) sleep = 8 to 10 hours/day), and then classified into three categories according to the combination of recommendations’ adherence: I) minimal adherence (only one behavior); II) partial adherence (two behaviors); III) total adherence (all three behaviors). The McNemar test was used to analyze whether adherence to the recommendations varied between the two time points. Results: The proportion of adolescents who met the recommendations at baseline and follow-up was 23.1% vs 35.1% (minimal adherence), 49.0% vs 52.1% (partial adherence), and 27.9% vs 12.8% (total adherence), respectively. Total adherence to the recommendations was higher at baseline compared to follow-up (P=0.009). No significant changes were observed between minimal and partial adherence over time. When analyzing behaviors individually, a significant reduction in adherence to the PA recommendations from baseline to follow-up was observed (70.4% vs. 39.9%, P<0.001). Conclusion: The proportion of total adherence to the 24-HMB guidelines in Brazilian adolescents is low and appears to decrease throughout adolescence.

Historically, university students develop harmful health-related habits that have negative consequences for current and future health outcomes. To begin tackling this issue, literature has previously identified relationships between psychological and behavioural markers of health. However, there is currently limited understanding of the system within which these factors interact. The current study aimed to explore the relationships between health-related behaviours and outcomes in UK university students using Bayesian network analysis. 4,132 university students completed an online, self-report survey to assess behavioural and psychological markers of health over three academic years (2021-2023). Directed Acyclical Graph (DAG) analysis was conducted to explore the relationships between variables of interest. The DAG demonstrated that ethnicity had the most profound influence on the model. Perceived stress (PS) also had a major impact on the model through directly influencing smoking status, sleep quality (SQ), and mental wellbeing (MWB). Body mass index (BMI) also had a notable impact via direct associations with SQ and movement behaviours. When separated by gender, the model in men was largely similar to the overall model. However, in women, the associations between smoking status and SQ, smoking status and SB, and BMI and SQ were no longer present. These findings provide novel insight into the complex system within which psychological and behavioural aspects of health interact to influence students’ health status. Specifically, targeting PS and BMI could be an effective strategy to improve various markers of health and behaviours in UK university students.

Background: The 24-hour movement guidelines recommend that screen time (ST) should be limited to ≤2 hours/day to maintain appropriate levels of health. However, in relation to cognitive abilities, such as working memory, different types of devices media have shown divergent results. Thus, the aim was analyze the interrelationships between screen devices and working memory, according to adolescents´ compliance with screen time guidelines. Methods: Cross-sectional data were collected from a sample of 153 adolescents (72 boys; 14.9 years-old). Self-reported ST for television (TV), video games (VG), smartphones, and leisure personal computer (PCL) were categorized based on compliance with screen time guideline (≤2 hours/day). Working memory was assessed thought the Corsi block-tapping test, by the block span (BS) measure. Additionally, cardiorespiratory fitness (20-m shuttle run test), body mass index (BMI), and maternal education level (self-reported) were recorded. Partial correlation networks and the expected influence centrality measure were calculated using the Network Analysis (JASP 0.18.3). Results: Overall, 54.9% of adolescents adhered to the screen time guideline and no significant differences were observed between genders (p>0.05). Boys spent more time (hours/day) on VG (2.00 ± 1.71 vs. 1.27 ± 1.38; p<0.05) and PCL (1.53 ± 1.80 vs. 0.65 ± 1.04; p<0.05) compared to girls. The network configuration identified that PCL and VG screen devices were positively associated with BS for the non-compliant adolescents. However, the same devices showed a negative association for those compliant with the guideline. Smartphone use (met ST: -0.451; do no met ST: 0.358) and BMI (met ST: 1.317; do no met ST: 1.610) were the variables with the highest expected influence values in both groups. Conclusion: These results support the idea that specific media devices may have a positive effect on working memory, however, this association is distinct when ST is limited.

29th Apr 2024

Parents play a crucial role in shaping a child’s physical activity, sedentary behaviour and sleep (i.e. 24-hour movement behaviours). However, inconsistent research findings on the relationship between parenting and these behaviours underscore the need for a nuanced understanding. Leveraging the Self-Determination Theory (SDT) as an organizing framework holds promise in clarifying this complex relationship. This study aims to investigate the relationship between parenting constructs conceptualized within the SDT and 24-hour movement behaviours in preschoolers.
This cross sectional study focuses on children between 2,5 to 5 years old and one of their parents. Data collection spans December 2023 to February 2024. The 24-hour movement behaviours will be measured for seven consecutive days using ActiGraph wGT3X+ accelerometers and processed by GGIR package in R. A questionnaire, encompassing the Parent Social Context Questionnaire-Toddlers, gauges parenting dimensions within the SDT framework. This includes warmth, autonomy support, structure, rejection, coercion, and chaos. Supplementary questions derived from the Movie Models study assess structure, autonomy support, and positive involvement specifically for each of the behaviours. Multiple compositional regression analyses will be employed in R, with significance set at p<0.05.
In total, 141 parent-child dyads are participating. Preliminary results (n=25) show 515.71 (SD=89.64) minutes of PA/day, 172.67 (SD=54.64) minutes of SB/day (p=0.752), and 623.08 (SD=44.64) minutes of sleep/day. Regression models will investigate which parenting constructs contribute to a more favourable 24-hour composition, characterized by increased physical activity, reduced sedentary behaviour, and sufficient sleep. The results will be available and presented at SSHB 2024.
A comprehensive understanding of the parenting constructs influencing a favourable 24-hour movement behaviour composition might provide actionable guidance for promoting healthier movement behaviours in preschoolers.

The influence of 24-hour movement behaviours (physical activity (PA), sedentary behaviour (SB), and sleep) on health is well-established. However, compliance with WHO guidelines for 24-hour movement behaviours among preschoolers remains low. Given the significant influence of parents on children’s health behaviours, an evidence- and theory-based intervention was developed in collaboration with parents to optimize preschoolers movement behaviours. This study aims to investigate the effect of a co-created intervention to optimize 24-hour movement behaviours in preschoolers.
Dyads of parents and their preschool child (2.5-5 years old) were recruited from Flemish preschools and were assigned to an intervention or a control group. Seven consecutive days of preschoolers’ movement behaviours were measured using ActiGraph wGT3X+ accelerometers and processed with the GGIR package in R. A socio-demographic questionnaire was completed by the parent. Baseline measurements were completed between December 2023 and February 2024 for both groups. The intervention, consisting of seven sessions for parents and preschoolers, is taking place between the end of February to mid-May 2024. Post-intervention data collection is scheduled from mid-May to June 2024. Compositional linear mixed models will be employed in R, with significance set at p<0.05, to assess intervention effects.
In total, 40 preschoolers in the intervention group and 90 preschoolers in the control group are participating. Preliminary data show no differences between the intervention and control group with averages of respectively 524.43 (SD=71.91) and 503.50 (SD=113.05) minutes of PA/day (p=0.389), 172.14 (SD=57.63) and 173.40 (SD=53.22) minutes of SB/day (p=0.752), and 626.79 (SD=44.57) and 617.90 (SD=46.62)minutes of sleep/day (p=0. 0.857). Linear mixed models will investigate intervention effects and whether the intervention contributes to a more favourable 24-hour composition, characterized by increased PA, reduced SB, and sufficient sleep.
The findings of this study will give insight in the efficacy of a co-created intervention in optimizing 24-hour movement behaviours in preschoolers. The results will be presented at the SSHB 2024 symposium and might provide guidance for promoting healthier movement behaviours in preschoolers.

The COVID-19 pandemic has raised alarming concerns regarding the diminished physical fitness and increased susceptibility to bone fractures among school children. The purpose of this study was to clarify the relationship between arch condition, toe formation, toe muscles, and the results of physical fitness test.
The subjects were 1,303 children (657 boys and 646 girls) aged 6 to 14 years in K town, N prefecture. The survey was conducted in May 2023. The survey items were height, weight, physical fitness test, toe muscle strength, and arch condition. In addition, foot length, foot width, and the mean and standard deviation of all items were determined for each school.
Results and Discussion
Results revealed a progressive increase in toe muscle strength and toe arch formation with advancing grades, albeit with a decline observed from the second year of junior high school onwards. Notably, elementary school students exhibited arch formation, particularly in suburban areas, highlighting potential regional disparities. Significant differences (<0.001) were found in various physical fitness test components between different grade levels and gender groups, suggesting nuanced patterns in physical fitness development. However, while toe muscle strength demonstrated a correlation with physical fitness test results, no significant difference was observed in relation to arch formation or excessive hallux valgus tendencies.
This study underscores the importance of understanding the multifaceted relationship between foot biomechanics, musculoskeletal health, and physical fitness in school children. Addressing these dynamics can inform targeted interventions to mitigate the adverse effects of reduced physical activity and promote overall well-being among children in the wake of the pandemic.

27th Apr 2024

Continuous lifestyle, physical fitness, and physical activity (PA) surveys are conducted in Japan. This study aims to clarify the changes in PAT of Japanese children over 20 years, analyzing data from two representative continuous surveys.
This study uses the following two survey results. One is the Student Health Status Surveillance (SHSS) conducted by the Japan School Health Association, which was conducted once every two years from 1992 to 2018. The target was 7,000 and 18,000 3rd- through 12th-grade students. PA time (PAT) survey was conducted based on the IPAC method in this survey. The distribution of PAT per week (DPAT) was obtained from 10 surveys from 1993 to 2010. The other is the Japanese national survey on physical fitness, motor abilities, and lifestyle (NSPML) conducted by MEXT, Japan, since 2008, which is a comprehensive survey targeting 5th- and 8th-grade students using the original PAT method. The DPAT was obtained from 2008 to 2016.
Results and discussion
In the initial SHSS survey, the DPAT had a left-skewed distribution with a peak of 4-10 hours. However, from around 2000, the proportion of inactive children showed a tendency to increase in all grades, shifting to a monotonically decreasing distribution. In addition, among high school boys, the 5-10 hours PA decreased, though the 10 hours or more PA increased, which indicated a polarization of active and inactive children. The trend has been observed among high school girls and middle school boys and girls since the 2004 survey. DPAT of NSPML also showed a similar trend to SHSS results. In the 2010s, the polarization of PAT became even stronger. Based on these results, DPAT on weekdays and weekends has been focused since 2017.
DPAT has changed over time, and a polarization between active and inactive children was confirmed, with these differences becoming more pronounced.

20th Apr 2024

Introduction: Integrating movement behaviours into the 24-hour recommendations is a holistic approach of leading a healthy lifestyle. However, research on how complying with each behaviour influences the others is still scarce. Therefore, this study aimed to explore the interconnectedness between attaining each of the 24-hour movement behaviour recommendations among Portuguese youth.
Methods: A total of 282 students (138 girls), aged 11 to 17 years old (mean=12.9±1.0), participated in this study. Young people’s movement behaviours, such as physical activity, sedentary behaviour (screen time) and sleep, were measured by accelerometery and self-reported. Logistic regression models were carried out to investigate the relationship between each of the movement behaviours, adjusting the analysis for gender and age.
Results: Sleep recommendations were attained by 64% (95% confidence interval [CI]: 58.2, 69.4) of youths. On the other hand, only 25% (95%CI: 20.1, 30.2) and 29% (95%CI: 23.8, 34.4) complied with physical activity and sedentary behaviour recommendations, respectively. Attaining the sedentary behaviour recommendations increases twofold the chances of complying with both the physical activity (odds ratio [OR]=2.03; 95%CI: 1.04, 3.97) and sleep recommendations (OR=2.33; 95%CI: 1.27, 4.26). Complying with the physical activity and sleep recommendations were not related to each other.
Conclusions: Compliance with the 24-hour movement behaviours recommendations among Portuguese youth is still far from ideal. Notwithstanding, attaining the sedentary behaviour recommendations was interconnected with physical activity and sleep recommendations. Public health strategies targeting youth’s screen time may also be effective for promoting physical activity and sleep.

19th Apr 2024

Introduction: Health-related fitness is an important biomarker of health in youth. However, information on the association between 24-hour movement behaviour compliance and the different health-related fitness parameters is still uncertain. Thus, the aim was to analyse the association between complying with the 24-hour movement behaviours and health-related fitness in Portuguese youth.
Methods: Participants were 263 Portuguese youths, 51.3% boys, with a mean age of 12.9±1.0. Movement behaviours (moderate-to-vigorous physical activity [MVPA], screen time and sleep) were assessed by accelerometers and self-reported. Health-related fitness was assessed using the FITescola battery, including body mass index (BMI), waist circumference (WC), aerobic fitness (PACER), upper-body strength (push-ups), lower-body strength (standing broad jump), agility (4x10m shuttle-run) and speed (40m dash). Linear regression models, adjusted for sex and age, were performed for each fitness parameter.
Results: Only 24.7% (95% confidence interval [CI]: 19.5, 29.9) and 28.5% (95%CI: 23.0, 34.0) of children and adolescents followed the MVPA and screen-time recommendations, while 64.6% (95%CI: 58.8, 70.4) attained enough sleep. Complying with MVPA was associated with better aerobic fitness (B=14.5 laps; 95%CI: 9.8, 19.1) and upper- (B=2.1 push-ups; 95%CI: 0.4, 3.7) and lower-body strength (B=10.9 cm; 95%CI: 3.8, 18.2). Whereas, attaining screen-time recommendations was related to lower BMI (B=-1.1; 95%CI: -2.1, -0.1). Sleep was not associated with any fitness parameter. Following all three movement behaviours was associated with better aerobic fitness (B=10.7 laps; 95%CI: 2.7, 18.7) and upper-body strength (B=2.8 cm; 95%CI: 0.1, 5.6) and thinner WC (B=-5.0 cm; 95%CI: -9.8, -0.2).
Conclusions: Movement behaviour compliance is associated with health-related fitness but with different patterns. While engaging in 60 daily minutes of MVPA seems key for muscular and aerobic fitness, having less than 2 hours/day of screen time may positively impact weight. Promoting the 24-hour movement behaviours could be a gateway for improving health-related fitness in future generations.

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