Perceptions and experiences of occupational sedentary behaviour and cardiometabolic responses to reducing sitting time at work

Abstract

Sedentary behaviour is linked to cardiometabolic health, independent of physical activity (PA), in a majority of the UK population. The workplace accounts for around 70% of daily sitting time, thus making it a popular domain for intervention. This thesis included a critical review and four studies which evaluated the use of sit-stand desks in relation to; perceptions and experiences; acute blood glucose responses; longerterm cardiometabolic health changes and self-reported use and finally the vascular health changes. Within this thesis a review of the literature was carried out, and examined evidence relating to occupational sedentary behaviour and its impact on health amongst adults, as well as the effectiveness of interventions to reduce occupational sitting time. The review highlighted that whilst many sit-stand desk interventions effectively reduced occupational sitting time, findings regarding both acute and chronic cardiometabolic responses to such interventions were equivocal. The review also highlighted that perceptions of sit-stand desk use are underinvestigated, particularly in the UK context. Study one used focus groups to examine the perceptions and experiences of sit-stand desk work amongst UK based officeworkers. Expected health beliefs and personal health history were important drivers of behaviour change whilst experienced benefits, organisational culture and peers were important in maintaining behaviour change. Study two examined the acute bloodglucose responses to sit-stand desk work using continuous glucose monitoring (CGM) and assessed changes to workplace sitting, standing and stepping time. Objectively measured workplace sitting time decreased by ~50% and total daily sitting percentage reduced from 70% to 45%. However there were no significant differences in postprandial blood glucose excursion between conditions. Occupational sitting time of this sample was much lower than that previously reported within the literature and may explain differences in findings. Study three examined a longer-term (6 and 12 month) intervention, assessing self-reported sitting time, self-reported physical activity and cardiometabolic health markers including anthropometric measurements, predicted aerobic capacity, blood pressure and blood profiles. Self-reported sitting time significantly decreased over 6 and 12 month interventions. A decrease was also seen in the control group prior to the intervention period suggesting a possible trial effect. Despite this change to self-reported sitting, there was no significant impact on cardiometabolic health markers. Study four explored the impact of an 8-week sit-stand desk intervention on flow-mediated dilation (FMD), blood pressure and blood profile whilst measuring fidelity to the intervention using both self-report and objective measures of PA and sitting time. There was a significant decrease in self-report total daily sitting time however, objectively measured sitting time and cardiometabolic health markers did not significantly differ over the intervention period. Moreover, a significant difference was observed between self-report and objectively measured sitting time at midpoint, in the intervention group only. To conclude, whilst sit-stand desks are an attractive means to work, which participants perceive to be of benefit physically, mentally and in their work performance, the installation of sit-stand desks in isolation does not appear to be a sufficient means by which to impact on longerterm occupational sitting time. Additionally, self-report methods may not be a suitable means to measure changes to sitting time during an intervention. Future research should aim to explore the behaviour change techniques effective in reducing occupational sitting time, whether interventions which successfully decrease occupational sitting time bring about cardiometabolic benefits and disparities between perceived and measured outcomes of sit-stand desk interventions on activity levels, health markers, and performance markers.