The global impact of preventable cardiometabolic and non-communicable diseases remains excessively high; however, low- to middle-income countries (LMICs) such as South Africa bear the greatest burden (World Health Organization 2018). Insufficient physical activity is still the main behavioural risk factor driving the increase in preventable diseases in South Africa. The demands on employee productivity are high, resulting in prolonged sedentary behaviour, particularly amongst clerical workers (Clemes et al. 2014a). Sedentary behaviour is defined as ‘awake’ activities with limited energy expenditure, while in a sitting, reclining or lying posture (Tremblay et al. 2017). Continuous time in sedentary activities is associated with increased risk of cardiometabolic diseases and inflammatory markers, independent of moderate-to-vigorous physical activity (Hadgraft et al. 2020). Domains of sedentary behaviour include time spent sedentary during occupation, transport and outside of working hours (Clemes et al. 2014b). Workers in office-bound occupations are at an increased risk of being sedentary for most of the occupation-related domain (Chau et al. 2010). A study demonstrated that employed individuals use motorised transport for an average of 0.63 ± 0.68 h/day (Clemes et al. 2014b). This study demonstrated that participants who sat for more than 80% of the workday had higher sitting times during motorised commuting compared with those who sat for < 58% of the workday (1.07 ± 0.98 hours per day vs. 0.35 ± 0.27 hours per day, respectively; p < 0.0001) (Clemes et al. 2014b). The adult working population in high-income countries has been found to accumulate sedentary behaviour whilst at work, during recreational time at home and during travel time (Chau et al. 2010). Compounded by sedentary activities outside of work, this accumulated sedentary behaviour may increase the risk for cardiovascular disease, type 2 diabetes and all-cause mortality beyond certain thresholds, even adjusting for physical activity (Patterson et al. 2018). Even in LMICs, worker productivity is becoming increasingly reliant on technology-based solutions with little need to move from the seated position for any tasks, which encourages sedentary behaviours (Gradidge 2017). The implications include limited employee productivity, mental health concerns, financial strain and increased absenteeism. It is therefore important to address sedentary behaviour in the workplace.

A study in a high income country demonstrated reductions in cardiovascular disease risk amongst obese office workers following an intervention to address high sitting time by introducing sit-stand desks rather than the introduction of more physical activity (Healy et al. 2017). This study was a multicomponent intervention, including organisational, environmental (sit–stand desks) and individual components, and significantly better improvements were observed in glycaemic control and insulin resistance in the long term (12 months) compared with the short term (3 months) (Healy et al. 2017). Other studies have shown that environmental interventions such as sit–stand desks, electric height adjustable workstations and active workstations (treadmill and cycle ergometer workstations) result in lower sitting time and improvements in work-related activities (Edwardson et al. 2018; Shrestha et al. 2018). Healthy messages, different from guidelines, help influence individuals into a feasible behaviour pattern (Latimer et al. 2010). The public and occupational health guidelines to lower sedentary time, for instance, are made more acceptable through appealing messaging, such as ‘move more and sit less during the day’ (Holtermann et al. 2020). Evidence shows that workplace interventions to reduce sedentary behaviour can be facilitated by healthy messaging to improve behaviour modification (Healy et al. 2017; Manini et al. 2015).

Commonly, the messages aim to persuade individuals that physical activity is appealing and achievable. These supplementary messages can take many forms and can be disseminated through a variety of messaging processes.

However, there is still a paucity of evidence on the effect of workplace health programmes to reduce sedentary behaviour (Hadgraft et al. 2020). Thus far, only one LMIC intervention study has demonstrated a drop in sedentary behaviour amongst office workers, by using tailored mobile text messages to interrupt sitting time (Dunning et al. 2018). Messages reminding the study participants in the intervention group to stand up and take regular short walks were sent every 20 min during working hours in the working week, for the duration of the 10-week trial. This pilot study did not show a change in anthropometry and cardiometabolic disease markers. Indeed, there is an urgent need to address the cardiovascular disease risk profile of South African workers (Patel et al. 2013), and the place of employment may offer the opportunity to develop programmes to improve worker health and wellness (Patel et al. 2010; World Health Organization 2018).

The aim of this study is to assess the effectiveness of standing desks and healthy messaging (from the authors) on the risk of cardiovascular disease and sedentary behaviour in a cohort of office-based workers and to explore their perceptions on the effectiveness of this intervention to lower sedentariness in the workplace. This manuscript will provide information on the framework used to answer the intended study aims.

The combined standing desk–healthy messages group (group 1) will be provided with an adjustable sit–stand desk. The desk is designed for placement on top of the participants’ existing workstation, providing the opportunity to transition from sitting to standing without interrupting productivity. Research assistants, qualified in exercise science, biokinetics or physiotherapy, will set up the participants’ workstations in the most appropriate ergonomic position. The correct configuration will therefore be individualised for each study participant. Participants will be visited weekly by the research assistants to examine the set-up, monitor usage and encourage standing-based work. The participants will be asked to break up extended sitting time by accumulating bouts of standing activity, short intermittent bouts of ≥ 10 min initially and then progressing to longer bouts of ≥ 30 min over the course of the intervention (Smith et al. 2017). Regular communication on the benefits of interrupting sitting will be emailed to the participants. The combined standing desk–healthy messages group will also receive health-promoting messages from the authors focussed on lifestyle behaviour modification through email, short message services and telephonic communication once a week during working hours. The participants in the control group (group 2) will continue using their ‘traditional’ workstations as usual.

All data for the RCT will be analysed using Stata Special Edition (SE) (version 14, Stata Corp, United States of America). Descriptive statistics will be used for comparing outcome data at baseline and change from baseline to follow-up between the intervention and control groups. Paired t-tests for within-group comparisons over time or their non-parametric equivalents depending on data distribution will be utilised. Comparison between groups will be made using analysis of variance or the non-parametric equivalent. Multivariable linear regression models will be used to determine if any of baseline study variables modulate these effects on the outcome variables (change in BMI, lipids, BP, HbA1c, VO_2max and sedentary behaviour). Significance will be accepted at an alpha level of p ≤ 0.05. The Consolidated Criteria for Reporting Qualitative Research (COREq) checklist will be used for reporting on the methodology, research team, study design and analysis, and study findings (Tong et al. 2007).

The study has received ethical approval from the Human Research Ethics Committee, University of the Witwatersrand (ethics certificate number M190224), as well as relevant authorities in the company, and is registered as a trial with the Pan African Clinical Trial Registry (PACTR201911656014962). The South African Medical Research Council has reviewed and awarded a Self-Initiated Research Grant for the study. Participants will be asked to sign informed consent before participating in the RCT. The study participants will be required to give written consent prior to participation in the focus group discussions. In addition, written consent will be sought from the study participants for the recording of the focus group discussions. The study participants will be reminded that participation in the study is voluntary and that the freedom to withdraw will not result in negative consequences.

Workers in office occupations are at increased risk of cardiovascular disease because of prolonged sedentary behaviour (Wolf et al. 2018). One approach to health promotion for the employed population is to address sitting in the workplace. A review of interventions shows that cardiovascular health can be improved through interventions that reduce sedentary behaviour (Dunstan et al. 2012; Edwardson et al. 2018; Hadgraft et al. 2020). The findings of this study will add to a limited body of evidence on addressing sedentary behaviour in the workplace and will be used to inform health-promoting policies and to develop models for disease prevention in the sub-Saharan African workforce. Furthermore, by addressing cardiovascular disease risk in the workplace, overall work-related job performance, productivity and absenteeism may be improved.

The study will be conducted in one setting, and although the study population is diverse in terms of gender, age and socio-economic status, the external validity may be limited.

In conclusion, this study will provide formative data on understanding sedentariness and the prevention of cardiovascular disease risk factors amongst workers in office-based occupations for further investigation.