The purpose of this randomized controlled trial is to investigate the short-term efficacy of reducing recreational screen-based media use on physical activity patterns, sleep, physiological stress in families at least one child between 6-10 years of age.

Today screen-based media devices are almost unavoidable in our everyday lives. The media landscape has changed markedly during the past decade with some of the main aspects being the introduction of new portable devices, social networks, and online streaming services. The current experimental evidence on the efficacy of reducing todays screen-based media use in free-living is scarce.

This randomized controlled trial will be carried out based on the experience from a recently conducted pilot study, which was a 2-arm randomized non-controlled trial. The purposes of the pilot study were to explore the feasibility of our recruitment protocol, 7-day measurement protocol and the degree of compliance to the intervention components; namely a heavy restriction in recreational screen time for a 2-week period, either timed (no screen after 18 pm) or time restricted (≤ 3 hours/week/person).

In the current trial, only the time restricted protocol will be included, compared to a control group. To investigate the short-term efficacy of the intervention, the participants will go through a 7-day measurement protocol at baseline and again, during the final week of the intervention period (follow-up).

Ninety-five families with at least one child between 6-10 years of age will be recruited. A randomly selected adult from each household will be invited to answer a questionnaire, also including an invitation regarding participation in the current randomized controlled trial. Invitations will be sent to the adults' digital mailbox (e-boks), which is an online solution where one can receive mail from e.g. Danish public authorities. Based on the answers in the survey a preliminary screening for eligibility will be conducted (see section on inclusion/exclusion criteria). Families who fulfill specific criteria in the survey and further criteria assessed during a phone conversation will be invited to participate in this randomized controlled trial. Families who wish to participate will, after completion of the baseline protocol, will be randomized to either the intervention group or the control group (see section on arms and interventions).

The intervention (reducing recreational screen-based media use) was designed using the core major and minor elements of Albert Bandura's Social Cognitive Theory; namely, based on the idea of reciprocal determinism of an individual's environment, personal factors and behavior. The intervention includes i) a preparation document and meeting with the parents with the purpose of planning the course of the intervention and prepare the parents to set goals and self-regulate; ii) handing over the families portable screen devices when possible with an alternative mobile phone in exchange, which can be solely used for calls and text messages, will be afforded to the participants; iii) installing monitor software on all computers (stationary and laptops) and tablets and smartphone if these could not be given up, and connect a monitor device to all televisions in each household; iv) using "intervention reminders" (social cues), which will be placed beside stationary screen-based media devices and at central positions in the household such as the dining table.

Inclusion Criteria:

• High amount of screen time according to self-report: In each household, at least one adult must be above the 40th percentile for self-reported screen-time during spare time based on what was reported in the survey ((characterized as high in this study).
• To be eligible for the measurements children in the household must be ≥ 4 and < 15 years old during the entire experiment period.
• Adults must work full time or be full-time students
• Adults and children who participates in the measurements must have the resources to remove all recreational- and work-/school-related screen-time in the late afternoon and evening hours and during weekend days, with a few exceptions (described in the "intervention" section below), for a period of 2 weeks (intervention length).
• The household must include at least one adult and one child 6-10 years of age at the time the survey was sent out, both of whom must consent to participate in the experiment.
• Participants must report that they consider the extent of their screen time an issue
• Participants must report to be particularly motivated to decrease screen-time for the whole family household.
• Members of the household who choose not to participate or who is ineligible to participate in the measurements or the intervention, must be willing to support the remainder of the household in making the experiment a success for them.

Exclusion Criteria:

• If the adults or children only reside in the household part time, e.g. have multiple addresses
• Prescribed a period of sick leave due to stress within the last 3 months.
• Diagnosis of sleep disorders from their general practitioner still interfering sleep
• Working night shifts
• In any shape or form limited in one's ability to engage in physical activities
• Neuro psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD) and autism