The purpose of the study is to test an intervention aiming to reduce sitting time during work hours among office workers.

Expectations according to outcome measures: Sitting time reduced by 1 hour pr. day (primary). Number of prolonged periods reduced by 1 pr. day (primary). Number of breaks increased by 3 pr. day (primary). 20 % of participants report a reduction of musculoskeletal pain (secondary). A reduction in waist circumference of 1 cm (secondary). A reduction of 0.5 % in bodyfat (secondary).

Background and aim: Sedentary behaviour has substantial impact on wellbeing and health, e.g. on the risk of cardiovascular disease and premature death. These associations seem to apply as well to people who carry out the recommended 30 minutes of physical activity per day. However, studies indicate that the harmful effects can be reduced through breaking prolonged periods of sitting by intervals of standing or walking.

In total 46 % of Danes are working in occupations which are primarily sedentary and the workplace is thus a relevant setting to intervene against sedentary behaviour.

The aim of the study is to test an intervention towards sitting time among office workers. The intervention will target both total sitting time, breaks from sitting and prolonged periods of sitting.

Design: Cluster-randomized control study led at four different workplaces in Denmark and Greenland. Each workplace should consist of four independent sections (clusters) of about 25 people. Those four sections are randomized to intervention or control. A cluster design is used because the intervention will target the workplace setting as a whole, thus individuals within the same office has to be randomized to the same arm of the intervention.

Participants: 400 adults with sedentary office-based work. Subjects should understand Danish and be without disabilities or diseases affecting their ability to stand or walk.

Intervention: Participating clusters are randomized to

1. Intervention: The intervention consists of four parts: Information, local adaptions, structural changes and individual support.
2. Control: The control group will receive the intervention after the last follow-up (about 3 months later).

Methods: Data on sedentary behaviour is collected objectively using ActiGraph. Waist circumference and body fat percentage is measured. Questionnaire data will be collected on background variables, physical activity level, workplace conditions and well-being.

Data will be collected at baseline, and after 1 and 3 months.

Analysis will be carried out following the intention-to-treat principle comparing the intervention and control group. We will use several outcomes and include baseline values as a covariate (ANCOVA). In addition we will use multilevel models to account for the hierarchical structure of data (workplace, cluster and participant).

Process evaluation will be conducted by the use of qualitative interviews and questionnaire data and concern both adoptions, implementation and sustainability of the intervention.

Inclusion Criteria:

1. Workplaces should be:

   • Office-based with sedentary workers
   • Able to include four sections of about equal size (about 25 people) and which could be separated to minimize spill-over effects (e.g. four different addresses, buildings or floors).
   • Have a management willing to collaborate about the project by participating at meetings and at kick-off.
   • Should have at least some financial resources to make structural changes at the work place.

2. Individuals should be:

   • Adults >18 years
   • Sedentary office-based work-
   • Understanding of Danish
   • Without sickness or disabilities affecting their ability to stand or walk
   • Not pregnant
   • Working more than 4 days a week (>30 h)

Exclusion Criteria:

• Not providing signed informed consent.