The importance of sitting less and moving more

Evidence of the importance of minimising sedentary behaviour to reduce risk of cardiovascular disease, type 2 diabetes,1 and premature mortality23 has accumulated rapidly in recent years. Although sedentary behaviour is largely independent of physical activity, being physically active has been shown to reduce some of the health risks associated with sitting too much.34 The latest UK5 and international6 physical activity guidelines therefore recommend limiting sedentary time by replacing sitting with periods of physical activity across the waking day.

Office workers spend much of their working day sedentary,7 meaning the workplace is an important site to intervene to encourage sitting less and moving more. Recent studies have shown promise for workplace interventions in decreasing time spent sitting.8910 However, almost all have largely focused on sitting at work and have neglected the opportunity to improve sedentary behaviour beyond the workplace.

In a linked paper, Edwardson and colleagues (doi:10.1136/bmj-2021-069288) report on a cluster randomised controlled trial of the SMART Work and Life (SWAL) intervention in local government council offices in England aimed at supporting staff to sit less and move more, not only at work but also outside working hours.11 SWAL is a theoretically informed, multilevel (organisational, environmental, group, individual) intervention delivered by workplace champions. It encourages participants to consider strategies to reduce their sedentary time and to break up sitting both at work and on non-workdays. A strength of the study design was allowing comparison of the effectiveness of the intervention with or without a height adjustable desk (SWAL only versus SWAL plus desk) to identify the unique contribution of the desk. A control group continued their usual practice.

The findings are noteworthy because they come from a fully powered cluster randomised trial with objective measurement of sedentary behaviour at three and 12 months. In addition, the use of workplace champions to deliver SWAL in 52 offices across three council areas maximises its potential for post-research roll out. The intervention was effective at reducing sitting time and in sustaining the changes made over 12 months. Importantly, the addition of the height adjustable desk improved sitting outcomes threefold: at 12 months, participants in the SWAL plus desk group reduced their sitting time by 64 minutes per day on average (relative to controls) compared with 22 minutes for the SWAL only group. However, despite participants being encouraged to consider strategies to help them sit less at home, no improvements in sedentary behaviour were seen outside work hours. Furthermore, workplace sitting was largely replaced by standing, despite the introduction of environmental restructuring such as relocating printers and wastepaper bins to try to support participants to move more.

Edwardson and colleagues’ study provides new evidence that provision of height adjustable desks may be important to deliver clinically relevant health benefits. A recent systematic review reported an increased risk of mortality in people who sit for more than 9.5 hours a day2; the SWAL plus desk intervention reduced mean sitting time from 10 hours at baseline to nine hours at 12 months. However, as almost 40% of baseline sitting occurred outside the workplace, there is clearly room for greater improvement. Previous research, including some work based studies, has reported reductions in non-workplace sitting.12 The move to more home based and blended patterns of working after the covid-19 pandemic is likely to increase workforce sedentariness.13 Therefore, understanding how to optimise occupational interventions to support people to sit less and move more around their home during both work and non-working hours is essential. Although the provision of height adjustable desks for the home office may be beneficial, it is unclear to what extent the improvements in sitting time shown in the current study would be retained in the absence of other intervention components. For example, interpersonal level components are likely to have contributed to the positive changes in sitting and standing related social norms observed in the SWAL plus desk group.

Finally, as with previous studies,8910 despite the SWAL intervention being designed to encourage more physical activity, most participants simply replaced sitting with standing. The importance of moving more has been highlighted by evidence showing that replacing sitting with standing has negligible effects on cardiometabolic risk biomarkers,14 but breaking up sitting with periods of even light physical activity seems to be beneficial for cardiometabolic health15 and mortality risk.16 Therefore, in addition to understanding how to better support people to move more in offices, opportunities to engineer movement into the home need further consideration to ensure that the often more confined home environment does not further restrict workers’ physical activity.