The study investigates whether a workplace intervention can encourage highly sedentary contact centre call agents to sit less and move more at work. The effect of the intervention will be assessed at 12 weeks and 9 months. The hypothesis is that the intervention will reduce workplace sitting and increase workplace standing and light walking.

Study Design:

This randomised controlled trial has two experimental treatment arms, SLAMM and SLAMM+.

Recruitment:

- Organisation Level:

Organisation recruitment is via a tender process. A recruitment infographic and application form will be emailed to contact centres affiliated with the Call North West Forum (~700 centres in the North West of England). Organisations have 3-weeks to apply by submitting the application form to the research team. Applications will be reviewed and ranked, and if multiple suitable organisations apply, a meeting will be held with each organisation to discuss the organisation's suitability. Applicants will be notified of the decision via telephone call and subsequent confirmation email, with feedback as to why they were unsuccessful (if applicable). The gatekeeper from the successful organisation will receive a gatekeeper participant information and consent form to sign prior to individual level recruitment.

- Individual Level

Call Agents: Study information sessions during work hours at the organisation, and an email containing a participant information sheet, will be used to recruit call agents. Agents have 2 weeks to express interest. Interested employees will be screened for eligibility using stated criteria via telephone or in person. If inclusion criteria are met, written informed consent will be obtained and baseline assessments scheduled. There will be no racial or gender bias in participant selection.

Stand Up Champions: During agent recruitment, agents will be told about the opportunity to be a stand up champion and have 2 weeks to express interest. There is no limit to the number of champions recruited.

Team Leaders and Management: A participant information sheet and consent form sent via email will be used to recruit team leaders (focus group), middle managers (focus group) and senior managers (interviews) for the process evaluation on intervention acceptability and feasibility at 12 weeks and 9 months.

Group Assignment:

Following baseline data collection, randomisation to the SLAMM or SLAMM+ arm will occur using a number generator by a member of the research team not involved in recruitment. The unit of randomisation will be at the individual level. The participants will be informed of the outcome of the randomisation via email.

Data Collection:

Participants will complete assessments at baseline, 12-weeks and 9 months. Individual assessments include surveys, cardiometabolic and anthropometric measures, and objective physical activity and sedentary behaviour monitoring. Individual assessments will take place within the participant's work site during work hours. Participants will be asked to fast for a minimum of 8 hours, avoid smoking and active transport on the morning of the assessment, avoid alcohol, tea or coffee intake for a minimum of 12-h prior to assessments, and avoid strenuous exercise for a minimum of 24-h prior to assessments. A sub-sample of participants from each treatment arm will be randomly selected to take part in focus groups at 12 weeks and 9 months to evaluate intervention acceptability and feasibility.

Sample Size:

Allowing for moderate drop out, the study aimed to recruit 30 participants per arm and retain 23 participants per arm. A sample size of 23 per arm would achieve 90% power (alpha 5%; two-tailed) to detect a minimum difference of 60 minutes/8-hour workday between arms for workplace sitting time (primary outcome: expected standard deviation of 60 minutes/day).

Analyses:

- Outcome evaluation:

Data will be analysed by an independent statistician (blinded to the treatment arms) using STATA (STATACorp LP) with the alpha level set at p≤0.05. For continuous outcomes, intervention effects and changes within groups will be estimated using linear mixed models. Models will include fixed terms for group (intervention 1/intervention 2), time (3 or 9 months), and group-time interaction, with potential confounders. Estimates of changes within groups, and differences between groups, will be obtained using marginal means and pairwise comparisons of marginal means of the outcome.

- Process evaluation:

Inductive thematic analysis will identify, analyse and explore themes from focus group and interview data on intervention acceptability and feasibility at 12 weeks and 9 months. Surveys will also assess intervention acceptability and feasibility at 12 weeks and 9 months.

- Economic evaluation:

The economic evaluation will be conducted from three perspectives. From the health sector perspective, trial-and model-based cost-utility analyses will be performed to show the cost of the intervention per quality adjusted life year. From the employer perspective, a cost-effectiveness analysis will be conducted to show the cost of the intervention per change in productivity. From the broader societal perspective, a cost-consequence analysis will be presented outlining all the costs and effects (in their natural units) which are incurred by the various stakeholders including the participants, and the participant's family and friends.

Call agents inclusion criteria:

• Full time member of staff (≥0.6 full time or part time equivalent worker in a permanent or temporary/agency position)
• Call agent job role
• Based onsite throughout the trial period
• Access to a work telephone and desktop computer with internet
• Ambulatory

Call agents exclusion criteria:

• Health problems that would impact ability to stand for 10 minutes at a time
• Planned absence >3 weeks during first 3 months of the trial
• Planned relocation to another workplace/site during the first 3 months of the intervention
• Pregnant