Changes in vascular function after a reduced sitting intervention

Rationale: Over the last years, physical inactivity has been identified as the major cause of death in Western society (2, 3). Despite recommendations for regular physical activity and promotion of exercise programmes, still a large proportion of the population does not meet these recommendations. Some years ago, epidemiologic studies have identified the association between sedentary behaviour (i.e. sitting and lying) and cardiovascular diseases or cardiovascular(CV) risk factors. Importantly, the detrimental impact of sitting time is not altered after correcting for exercise training time. Therefore, the benefits from “reduce sitting time” and exercise training seem independent from each other. Consequently, prolonged sitting is a logical target to improve cardiovascular risk factors via reduced sitting time. The first short term studies (i.e. hours and weeks) have revealed benefits in several CV risk factors. In this study, we will explore the longer term effects of a reduced sitting intervention on CV risk, and (cerebro)vascular factors.

Objective: In this intervention study we examine the effect of a 12-week reduced sitting time intervention on cardiovascular function (i.e. changes in femoral artery FMD) in subjects with an increased risk for cardiovascular disease. As a secondary objective, we want to obtain insights in the cerebrovascular effects of a reduced sitting intervention. Therefore, we will measure cerebrovascular function and peripheral vascular function. In addition, we will investigate the mechanism involved in mediating the impact of prolonged sitting on vascular function by exploring measures of inflammation, NO-pathway and metabolism.

Study design: stepped wedge design

Study population: We will recruit 30 individuals, who spend >40 hours per week sitting and <120 minutes of moderate-intensity exercise (or <75 minutes of vigorous-intensity exercise) per week. An increased risk for cardiovascular disease was defined as those older than 45 years (men) or 55 (women) and presence of at least 1 cardiovascular risk factor.

Intervention (if applicable): 12 weeks reduced sitting intervention: Subjects will wear a pedometer throughout the day in order to record physical activity patterns. The device identifies prolonged periods of sitting or physical inactivity, which will lead to notification that the participant has to break up his/her sitting behaviour to reduce sitting time.

Main study parameters/endpoints:

1) Peripheral vascular function

2) Cerebral autoregulation

Vascular function improves after a reduced sitting intervention

Baseline, 12 weeks control period, 12 weeks intervention

Reduced sitting intervention: throughout the day participants prevent prolonged (i.e. >30 min) seated behaviour. This will be accomplished by a pedometer, which records physical activity levels. This device has been used by several previous studies and is validated to measure sedentary behaviour and physical activity (35-37). After a period of prolonged sitting (i.e. 30-minutes), participants receive an alert (i.e. vibration of the wristband). Participants then break up their sitting time and replace it by a few minutes of low to moderate intensity exercise, such as standing and walking. We aim to reduce sitting with 90 minutes per day, and increase sit-to-stand transitions with 5 per day, as is in line with the improvement in comparable intervention studies (18, 38, 39).