Background: The prevalence of low well-being, perceived stress and unhealthy behaviours is high among high school students, but few interventions have addressed these problems. The aim of this paper is to present a study protocol of a cluster randomised controlled trial evaluating the Healthy High School (HHS) intervention programme. The intervention programme is designed to improve well-being (primary outcome) by preventing 1) stress and promoting 2) sleep, 3) sense of community, 4) physical activity (PA) and 5) regular and healthy meals among high school students in Denmark. Methods: The development of the HHS study was guided by the Intervention Mapping protocol. The intervention comprises four components: 1) a teaching material, 2) a smartphone app, 3) a catalogue focusing on environmental changes, and 4) a peer-led innovation workshop aiming at inspiring students to initiate and participate in various movement activities. The HHS study employs a cluster-randomised controlled trial design. Thirty-one high schools across Denmark were randomly allocated to intervention (16 schools) or control (15 schools) groups. The study included all first-year students (~16 years of age) (n = 5976 students). Timeline: Intervention: August 2016-June 2017. Collection of questionnaire data: Baseline (August 2016), 1st follow-up (May 2017) and 2nd follow-up (April 2018). All students were invited to participate in a monthly sub-study about perceived stress using text messages for data collection (September 2016-June 2017). PA was objectively assessed among a sub-sample of students using accelerometers (Axivity, AX3) in August 2016 and May 2017. Primary outcome measures: Student well-being measured by the Cantril Ladder and the five item World Health Organisation Well-being Index (individual level outcomes). Secondary outcome measures: Stress (10-item Perceived Stress Scale), sleep (quantity and quality), PA (hours of moderate-to-vigorous PA per week, hours of daily sedentary time and average daily PA), meal habits (daily intake of breakfast, lunch, snacks and water), and strong sense of community in class and at school, respectively (individual level outcomes). The study encompasses process and effect evaluation as well as health economic analyses.

Health-promoting initiatives focusing on physical activity include advice on integrating active behaviour into everyday activities pointing to a tendency to combine a health agenda with other agendas. From a public-health perspective this might be a valuable strategy, but it calls for a conceptual awareness and exploration of the target groups' perceptions of this broader concept of physical activity. Nested in a Danish intervention study aimed at increasing wellbeing among high-school students aged 16-17 through the promotion of movement, this study engages in a conceptual exploration of 'movement in everyday lives' related to well-being. Combining participant observation and photo-elicitation interviews, the study investigates different kinds of meaning experienced in relation to movement. Theoretically, the study is framed by existential phenomenology with a focus on corporeality, temporality and intersubjectivity. An existential theory of well-being is applied to a discussion of the relationship between bodily movement and well-being. The findings point to movement as a way for students to balance two existential modes within the dimensions of corporeality, temporality and intersubjectivity: one of activity and tenseness, and one of break and stillness. For the students, movement entails bodily experiences ranging from modes of selfforgetfulness to the body demanding attention in different ways; they experience movement as a break from everyday obligations, but also as a way of moving forward; and they experience movement as an occasion for being social and for withdrawing from the social worlds.

Background Child mental health problems are a major public health concern associated with poor mental and physical health later in development. The study evaluates a new community-based intervention to promote sensitive parenting and reduce enduring mental health problems and unhealthy weight among vulnerable infants aged 9-24 months. Methods We use a step-wedge cluster randomized controlled trial design conducted within a home visiting program offered by community health nurses to infant families in Denmark. Sixteen municipalities are randomly allocated to implement the intervention starting at three successive time points from May 1, 2022 to January 1, 2023. A total of 900-1000 families will be included. A standardized program, Psykisk Udvikling og Funktion (PUF), is used to identify infants with major problems of eating, sleep, emotional or behavioral regulation or developmental problems. The intervention builds on the Video-Feedback Intervention to Promote Positive Parenting (VIPP) program, adapted to the PUF-context and named the VIPP-PUF. Children will be followed up at ages 18 and 24 months. Primary outcome measure is the Strengths and Difficulties Questionnaire (SDQ) at child age 24 months. The other outcome measures include body mass index z-scores, the Ages and Stages Questionnaire Social-Emotional (ASQ:SE2); the Child Behavior Checklist (CBCL 1½ -5); Eating behavior Questionnaires; the Being a Mother-questionnaire (BaM13); the Parental Stress Scale (PSS); and the WHO-5 well-being index (WHO-5). Data on child and family factors are obtained from National registries and the Child Health Database. Quantitative measures are applied to examine the effectiveness of the VIPP-PUF intervention and the implementation process. Qualitative measures include interviews with CHNs, parents and municipality stakeholders to explore factors that may influence the adherence and effectiveness of the intervention. Discussion The study examines a service-setting based intervention building on the promotion of sensitive parenting to vulnerable infants. We use a mixed methods approach to evaluate the intervention, taking into account the influences of COVID-19 pandemic running since March 2020. Overall, the study has potential to add to the knowledge on the possibilities of prevention within the municipality child health care to reduce the risk of mental health problems and unhealthy weight in early childhood. Trial registration www.ClinicalTrials.gov; IDNCT04601779; Protocol ID 95-110-21307. Registered 25 June 2021.

Summary Peer-led interventions are highlighted as promising strategies to promote health among adolescents, but little is known about the mechanisms underlying this approach. To better understand the role of peer mentors (PMs) as implementers in school-based health promotion, we combined participant observations, focus group interviews and video recordings to explore high school students’ reception of a peer-led intervention component (Young & Active). Young & Active aimed to increase well-being among first-year high school students (∼16 years of age) through the promotion of movement and sense of community and was implemented during the school year 2016–2017 in a larger school-based intervention study, the Healthy High School study in Denmark. The Healthy High School study was designed as a cluster-randomized controlled trial with 15 intervention schools and 15 control schools. At each intervention school, university students in Sports Science and Health (members of the research group) facilitated an innovation workshop aiming at inspiring all first-year students to initiate movement activities at schools. The findings illustrate potentials and challenges implied in the PM role. The peer mentors’ profound commitment, as well as their response and sensibility to situational contingencies, were found to be significant for the students’ reception and experience of the intervention. In conclusion, the specific job of PMs as implementers seems to consist of simultaneously following a manual and situationally adjusting in an emerging context balancing commitment and identification to the target group and the intervention project.

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