Associations between quality of life, physical activity, and sedentary behaviour : an examination of continuous and bout measures of activity and sedentary behaviour from the Walk 2.0 trial

Objective: The health benefits of physical activity participation and minimising sedentary behaviours are well known. As well, evidence exists for the relationship between physical activity and health-related quality of life. Research addressing these questions, however, has predominantly focused on continuous physical activity and sedentary behaviour measures, and has paid less attention to frequency measures (e.g., bouts of participation or sedentary time). The purpose of this study was to compare a continuous duration measure of physical activity and sedentary time with a frequency measure (number of bouts ≥10 min), and to test for associations of each with health-related quality of life. Methods: Baseline data from the Walk 2.0 Study were used for analysis in this study. The Walk 2.0 Study is a randomised controlled trial investigating the effects of Web 2.0 applications on engagement, retention, and subsequent physical activity behaviour change. Participants (N = 506) were 50.8 ± 13.0 years old and had a BMI of 29.3 ± 6.0. Physical activity and sedentary behaviour were measured using ActiGraph GT3X activity monitors and health-related quality of life was assessed with the RAND 36-item Short Form Health Survey (SF-36). Multiple regression models were used to test relationships of the continuous and bout measures of physical activity and sedentary behaviour with quality of life. Results: Participants engaged in 23.9 ± 18.1 minutes across 0.6 ± 0.7 physical activity bouts and 535.5 ± 82.3 minutes across 17.0 ± 3.4 sedentary behaviour bouts daily. Of the eight quality of life subscales, six were not significantly associated with either the continuous or bout measure of physical activity or sedentary behaviour. General health was negatively associated with the continuous measure (β= -0.29) and positively associated with the bouts measure (β = 0.22) of sedentary behaviour, but the interaction term between the two measures was not significant. Physical functioning was positively associated with the continuous physical activity measure (β = 0.22) but not with the bouts measure (β = -0.06). Conclusions: It is important to consider both duration and frequency (bout) measures of physical activity and sedentary behaviour, as both have differential impacts on health-related quality of life