A Mixed-methods Evaluation of Sit-stand Workstations in an Office Setting

NCT ID: NCT02496507

Last Updated: 2015-07-14

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 47 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2013-08-31
• Study Completion Date: 2013-12-31

Brief Summary

The purpose of this study is to investigate whether a device that allows office workers to sit or stand whilst working can reduce their sitting time at work and improve their health over 8 weeks.

Detailed Description

Study design

Treatment arms in this two-arm parallel-group randomised controlled trial (RCT) included a sit-stand workstation intervention group (each participant received a sit-stand workstation) and a control group (usual practice).

Recruitment

• Organisation level

Office workers from one organisation were targeted by the research team in August-September 2013. Consent was sought from 11 departmental managers for employee recruitment, installation of sit-stand workstations, study contact and laboratory visits during work time. Departments were located across four buildings with varying office layout (open-plan, individual offices or a combination). Employees within the targeted departments were predominantly administrative staff.

• Individual level

Via an email from the research team, all employees in consenting departments received an overview of the study and participant information sheet, and were invited to a study information session (two sessions were organised per department). Employees were given 2 weeks to express interest. Interested employees were screened for eligibility using stated criteria by the research team via telephone. If inclusion criteria were met, written informed consent was obtained and baseline assessments scheduled. There was no racial or gender bias in the selection of participants.

Group assignment and Intervention

Following baseline assessments, participants were assigned by one member of the research team to a treatment arm using a randomised block design and random number table. Departments served as blocks and participants within departments were randomly assigned at the individual-level to an arm. Assignment of individual participants within each department alternated between arms (i.e. intervention, control, intervention, control…).

Data collection

At baseline, 4 weeks (mid-intervention) and 8 weeks (end-intervention), participants' office-based behaviours were assessed via ecological momentary assessment (EMA) diaries. At baseline and 8 weeks, participants attended University laboratories in the morning for individual assessments of other stated outcomes. Prior to laboratory visits, participants were required to fast for a minimum of 8 hours, avoid the consumption of alcohol for 12 hours, and avoid strenuous exercise for 24 hours.

Sample size

Allowing for small drop out, the study aimed to recruit 25 participants per arm, and retain 23 participants per arm. A sample size of 23 per arm was chosen a priori to 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 SD of 60 minutes/day). Data collection for vascular and metabolic outcomes would provide effect size estimates for power calculations in subsequent trials.

Statistical analyses

• Data was analysed using the Statistical Package for the Social Sciences (SPSS) version 22 (IBM, New York, USA) with the alpha level set at p≤0.05. Intervention effects were compared at 4 weeks (sitting, standing and walking) and 8 weeks (all outcomes) from baseline using analysis of covariance (ANCOVA). The variable change score (4 or 8 weeks minus baseline) was the dependent variable, with intervention arm (control vs intervention) the independent variable. In all analyses, covariates were the baseline value for the variable to control for any imbalances at baseline. Anthropometric, sociodemographic, work-related and office-environment characteristics were tested as potential confounders for all outcomes. Confounders were entered as covariates if significant associations (p≤0.05) were observed with changes in an outcome and the effect on the mean difference between groups exceeded 20%. For changes in sitting, standing and walking time, baseline values of the other two behaviours were tested as potential confounders, though no effects on the mean difference between groups exceeded 20%. Adjusted change scores and 95% confidence intervals (CIs) for the difference in change between groups are presented unless stated otherwise. Acceptability and feasibility data are reported as medians and quartiles.
• Missing data and Intention-to-treat analysis Due to participant withdrawal, lost EMA diaries or the inability to conduct assessments, data were missing for all outcomes. Accordingly, a per-protocol analysis was conducted and participants were excluded from analyses for outcomes they were missing data for. For workplace sitting, standing and walking, the per-protocol analysis was compared with an intention-to-treat analysis, as a sensitivity analysis. To treat missing data, the fully conditional imputation technique and ten imputation sets were used due to a low rate of missing data. Imputation was based on all 47 randomized participants.
• Minimum important differences analysis Inferential statistics were ran using minimum clinically important difference principles, described elsewhere. Briefly, this approach makes inferences based on meaningful magnitudes and is recommended alongside hypothesis testing. A spreadsheet computed the quantitative and qualitative probability that the true effects were beneficial, trivial or harmful, after the outcome statistic, its p value, and the smallest/minimal important difference was entered. Minimum important differences for sitting and standing were 60 minutes/day, and for walking 10 minutes/day. Minimum important differences for other outcomes were determined through a distribution-based method as a Cohen's d (standardized difference between change scores between groups) of 0.2 between-subjects standard deviations (SDs). The SD of pooled baseline data was used to negate the possibility of individual differences from the intervention influencing the SD at 8 weeks. For each effect at 8 weeks, quantitative probabilities for benefit, trivial and harm, and qualitative descriptors are reported. Effects were interpreted as unclear if probabilities for benefit and harm were >5%.

Conditions

Physical Activity

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Intervention

Provision of a sit-stand workstation for use at work.

Group Type: EXPERIMENTAL

Sit-stand workstation

Intervention Type: OTHER

After baseline, each participant had a sit-stand workstation installed on their existing workplace desk. A single or dual monitor WorkFit-A with Worksurface+ workstation was installed, dependent on the number of monitors. The monitor(s) and keyboard were housed on the workstation and the workstation could be quickly raised up and down by hand to enable seated or standing work. Participants were not prescribed an amount of time to use the station. Ergotron Ltd provided and installed the workstations and gave participants basic face-to-face training and ergonomic information on correct use. Participants received a web link to manufacturer ergonomic guidelines via an email from the research team. After end-intervention data collection, manufacturer staff uninstalled the workstations.

Control

Participants were asked to maintain their normal work practices and received no intervention. Participants were offered the opportunity to have a sit-stand workstation installed for 8 weeks after all data collection.

Group Type: NO_INTERVENTION

No interventions assigned to this group

Interventions

Sit-stand workstation

After baseline, each participant had a sit-stand workstation installed on their existing workplace desk. A single or dual monitor WorkFit-A with Worksurface+ workstation was installed, dependent on the number of monitors. The monitor(s) and keyboard were housed on the workstation and the workstation could be quickly raised up and down by hand to enable seated or standing work. Participants were not prescribed an amount of time to use the station. Ergotron Ltd provided and installed the workstations and gave participants basic face-to-face training and ergonomic information on correct use. Participants received a web link to manufacturer ergonomic guidelines via an email from the research team. After end-intervention data collection, manufacturer staff uninstalled the workstations.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• full-time member of staff
• access to a work telephone and desktop computer with internet

Exclusion Criteria

• have a cardiovascular or metabolic disease
• taking any medication
• pregnant
• planned absence > 1 week during the trial

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Liverpool John Moores University

OTHER

Sponsor Role: lead

Responsible Party

Lee Graves

Lecturer/Senior Lecturer

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Lee EF Graves, PhD

Role: PRINCIPAL_INVESTIGATOR

Liverpool John Moores University

Locations

Liverpool John Moores University

Liverpool, Merseyside, United Kingdom

Countries

United Kingdom

References

Batterham AM, Hopkins WG. Making meaningful inferences about magnitudes. Int J Sports Physiol Perform. 2006 Mar;1(1):50-7.

Reference Type: RESULT

PMID: 19114737 (View on PubMed)

Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine and exercise science. Med Sci Sports Exerc. 2009 Jan;41(1):3-13. doi: 10.1249/MSS.0b013e31818cb278.

Reference Type: RESULT

PMID: 19092709 (View on PubMed)

E F Graves L, C Murphy R, Shepherd SO, Cabot J, Hopkins ND. Evaluation of sit-stand workstations in an office setting: a randomised controlled trial. BMC Public Health. 2015 Nov 19;15:1145. doi: 10.1186/s12889-015-2469-8.

Reference Type: DERIVED

PMID: 26584856 (View on PubMed)

Other Identifiers

15-SPS-Graves1

Identifier Type: -

Identifier Source: org_study_id