Protocol for the Work Engagement and Well-being Study (SWELL): a randomised controlled feasibility trial evaluating the effects of mindfulness versus light physical exercise at work

The study addresses whether mindfulness-based programmes (MBPs) improve workplace performance and through which mechanisms. Prior evidence supports MBPs for improving mental well-being, but effects on work performance are inconsistent and rarely measured directly. Two hypothesised pathways may explain benefits: (1) indirect effects via improved mental health and well-being, and (2) direct effects via enhanced cognitive control (shifting, updating, inhibition), particularly over emotional information. To isolate the cognitive control pathway, the trial compares a 4-week online mindfulness course to a time- and contact-matched 4-week light physical exercise course, as both may reduce stress, anxiety, and depression, but only mindfulness is expected to enhance cognitive control. The feasibility RCT aims to estimate effect sizes for work performance, explore mechanistic pathways, and assess acceptability and procedural feasibility in workplace settings.

- Mental ill health is a major contributor to work-related ill health and economic burden in the UK (~£45 billion/year). Employers increasingly deploy programmes to improve well-being and productivity.\n- MBPs reduce symptoms of anxiety, depression, and stress, and improve well-being, life satisfaction, and quality of life in community and nonclinical settings.\n- Evidence that MBPs improve work performance is limited and heterogeneous; performance is rarely assessed and definitions vary (engagement, motivation, absenteeism/presenteeism, error rates, burnout), hindering meta-analytic synthesis. In higher education, mindfulness does not clearly improve academic performance.\n- Mechanisms: Improved mental well-being is associated with better performance; mental health problems reduce performance, suggesting a potential indirect pathway. MBPs may also improve cognitive control (shifting, updating, inhibition). Meta-analyses report small effects of MBPs on executive control (Hedges' g≈0.2). However, most studies assess control over neutral stimuli; everyday workplace cognition often involves emotional material. Emotional stimuli can impair response inhibition (Stop-Signal Task). Mindfulness trains disengagement and decentring from negative thoughts, potentially enhancing affective cognitive control. Few RCTs have assessed cognitive control with emotional stimuli, and existing evidence is underpowered.\n- Understanding mechanisms can enable targeted intervention design, rigorous outcome selection, and identification of subgroups and contexts where MBPs are most effective.

Design: Participant-level, parallel-group, randomised controlled feasibility trial conducted fully online. Allocation 1:1 to mindfulness or light physical exercise. Primary endpoint: postintervention (immediately after 4-week courses), with 12-week follow-up to assess feasibility for a later definitive trial.\nSetting and participants: Employees from collaborating UK employers (local councils, education providers, and companies in publishing, electronics, construction), predominantly desk-based roles. Eligibility: employed by participating employers, UK-based, not on long-term leave. Recommended not to participate if currently suffering severe anxiety/depression/hypomania/mania or other severe mental illness, recent bereavement/major loss, or prior mindfulness course/meditation >10 hours in past 10 years.\nInterventions:\n- Mindfulness (Intervention): Be Mindful prerecorded online course (Wellmind Media), 4 weeks, 10 sessions, elements from MBSR and MBCT. Includes brief videos, self-reflection, formal meditations (10–30 min/day) and informal practices (eg, mindful walking/eating). Weekly release with reminder emails (four/week). Pragmatic adherence—no additional adherence-enhancing procedures.\n- Light physical exercise (Control): Prerecorded 4-week online course of light mobility/aerobic exercises (joint rotations, stretching) to reduce stiffness and improve circulation suited to sedentary tasks. Designed to match overall time commitment and frequency of contact (daily short videos ~10–13 min; daily practice prompts; four reminders/week).\nData collection timeline: Baseline (T0), postintervention (T1, primary endpoint), and 12-week follow-up (T2/T3 per figure; end of Week 17). Daily brief work performance measure each workday during intervention.\nOutcomes:\n- Feasibility/acceptability/procedural: between-arm effect size estimates (primary and cognitive outcomes); recruitment rates; retention and timing of measurements; contamination (cross-arm discussions); acceptability (allocation preference, practice regularity, dose/percentage of materials attempted); suitability of primary measure vs other work-related outcomes; potential covariates (baseline mental/physical health; job-identity importance).\n- Primary outcome: Work performance via Work Role Functioning Questionnaire (WRFQ, 25-item, updated version). 5-point scale; higher scores indicate better functioning; four subscales (work scheduling/output, physical, mental/social, flexibility demands). Primary endpoint at postintervention; feasibility of 12-week endpoint assessed.\n- Secondary work-related outcomes: self-reported health conditions affecting work (physical/mental/other/none); Work and Social Adjustment Scale for those reporting problems; daily 5-item WRFQ each workday afternoon.\n- Mechanisms (cognitive control): Emotional Stop-Signal Task (negative/neutral image primes; go/stop trials; main outcome: stop-trial response time; also RTs, accuracy, RT variability). Affective probabilistic reversal learning task (neutral/negative conditions; learning under changing contingencies; main outcome: proportion correct across phases).\n- Other outcomes: Well-being (SWEMWBS); stress (Perceived Stress Scale-10); depression (PHQ-9); anxiety (GAD-7).\n- Mindfulness-related checks: Decentring (Experiences Questionnaire); trait mindfulness (MAAS).\nSample size: Aim to recruit n=240, anticipating ~47% attrition at postintervention (targeting ~128 complete cases; ~64/arm) and ~68 at 12-week follow-up (~34/arm). Purpose is to estimate effect sizes and assess feasibility rather than hypothesis testing.\nRecruitment and incentives: Employer-led invitations via internal channels; participants receive £10 (postintervention) and £15 (follow-up) retail vouchers for completing assessments. No inducements for intervention adherence.\nRandomisation and blinding: Automated in REDCap, stratified by employer, using permuted blocks (seeds pre-specified; code on GitHub). Participants unblinded; primary analysis by a statistician blinded to allocation.\nStatistical analysis: Descriptive summaries (central tendency, dispersion, missingness) at all time points. Primary analysis: linear multiple regression comparing postintervention WRFQ total between arms, adjusted for baseline WRFQ and employer; multiple imputation for missing data. Exploratory analyses for other outcomes at post and 12-week follow-up. Mediation analyses to evaluate mechanistic pathways. Daily work performance analysed via mixed-effects repeated measures to compare arms and compare work performance measures. Focus on effect sizes, not statistical significance. Intention-to-treat principle applied where relevant.\nData monitoring and safety: Independent Study Steering Group. Safeguards include optional consultation with a clinical psychologist; automated alerts for high PHQ-9 (≥20 or self-harm item >0) or GAD-7 (≥15), followed by clinician contact; tracking reasons for withdrawal; attribution of adverse events determined by the steering group.\nEthics and data management: Approved by Cambridge Psychology Research Ethics Committee (PRE.2020.072). Electronic informed consent procedures with information on support services. Data collected via REDCap, Cohort Management System, and JATOS; personally identifiable information stored separately on encrypted servers; anonymised data shareable on request per open science principles. Dissemination via peer-reviewed journals and lay summaries to employers/participants.

- Feasibility trial not powered to detect statistically significant effects; focus is on estimating effect sizes to inform a later definitive trial.\n- Potential high attrition inherent to fully online workplace RCTs may limit completeness of outcome data.\n- Risk of contamination (participants discussing interventions across arms) in workplace settings.\n- Primary outcome measure (WRFQ) lacks prior validation in English, although validated in other languages; suitability as the primary endpoint is being assessed.\n- Short intervention duration (4 weeks) and 12-week follow-up may not capture longer-term effects or sustainability.\n- Heterogeneity across participating employers and roles may introduce variability affecting generalisability and effect estimation.