Understanding and increasing transport-related physical activity : evidence from observational and interventional research

Background:
The domain of transport-related physical activity has been identified as a means of increasing total physical activity levels due to its habitual nature. However, little is understood regarding what drives individuals to undertake transport-related physical activity, how transport-related physical activity changes across the lifecourse, and how transport-related physical activity levels may best be increased.
Aims:
The overall objective of this thesis was to create evidence to guide the development of evidence-based strategies to promote transport-related physical activity behaviours across the lifecourse.
This thesis first aimed to gain a greater understanding of the factors associated with adult transport-related physical activity through the systematic review and synthesis of studies published across the past decade. Second, using an Australian study, this thesis aimed to understand the transport-related physical activity behaviours across the lifecourse, determining whether transport-related physical activity behaviours observed in childhood influence those experienced in adulthood. Third, the patterns and pathways through which factors associate with transport-related physical activity at different periods across the lifecourse (childhood, young -adulthood, early adulthood, and mid-adulthood) were examined. Finally, this thesis aimed to determine the utility of a financial incentive-based public transport intervention in the promotion of transport-related physical activity via habitual integration.
Methods:
The first aim of this thesis was addressed via the systematic review of English, peer-reviewed literature from 2010 to 2020, quantitatively examining factors associated with the outcome of adult transport-related physical activity. Data from the Childhood Determinants of Adult Health (CDAH) Study was used to address aims two and three. The CDAH study, a follow-up of the Australian Health and Fitness Survey, examined via surveys and clinics the health and physical activity of participants at four timepoints across the lifecourse: 1985 baseline (aged 7-15 years), early-adulthood (2004-2006; aged 26-36 years), early/mid-adulthood (2009-2011; aged 31-41 years), and mid-adulthood (2014-2019; aged 36-49 years).
To determine the utility of a financial incentive on the promotion of transport-elated physical activity (aim four) data from the Australian trips4health study was used. The trips4health study was a single-blinded randomised control trial of an incentive-based intervention involving adult infrequent bus users. Accelerometer-measured steps/day (primary outcome), self-reported total and transport-related physical activity outcomes were assessed at baseline and follow-up.
Results:
The systematic review of the correlates and determinants of adult transport-related physical activity found seven individual, social, and environmental factors to demonstrate consistent association with higher transport-related physical activity: lower socio-economic status, higher self-efficacy, higher social normalisation, lower distance of travel, higher destination concentration, more streetlighting, and higher public transportation frequency with a greater number of terminals near route start and endpoints.
Analysis of lifecourse trajectories of transport-related physical activity in the CDAH study found that childhood transport-related physical activity levels were not associated with transport-related physical activity patterns in adulthood. Two stable transport-related physical activity trajectories were identified across adulthood: persistently low (73.5 %), and increasingly high (26.5 %). While childhood transport-related physical activity may have may health, social, and environmental benefits, these findings suggest that further intervention is required beyond childhood to promote healthy transport-related physical activity behaviours into adulthood.
Modelling of pathways of direct and indirect association between covariates and transport-related physical activity in the CDAH study found a number of pathways to be consistent across the lifecourse. In childhood, greater age, urban residence, and better self-rated health were directly associated with greater levels of transport-related physical activity. Furthermore, self-rated health was also found to be directly associated with transport-related physical activity across all adult timepoints. During periods of early-, early/mid-, and mid-adulthood, consistent indirect pathways of effect were observed with greater body mass index and smoking frequency leading to poorer self-rated health and resultantly lower levels of transport-related physical activity. Similarly, those with lower education levels smoked more frequently, rated their health poorer, and undertook less transport-related physical activity at all adult timepoints.
Using the trips4health randomised control trial, this analysis found evidence that a financial incentive-based intervention to increase public transport use is effective in increasing self-reported transport-related physical activity among the intervention group, but not accelerometer measured daily steps or total physical activity levels.
Conclusion:
This thesis addressed important gaps in the knowledge by identifying the patterns and pathways of transport-related physical activity across the lifecourse, providing a detailed synthesis of the factors that influence transport-related physical activity, and by determining the utility of a financial incentive-based intervention to increase transport-related physical activity levels. Through systematic review, longitudinal observational analyses, and an intervention study, this thesis presents potential targets that inform and support researchers, practitioners, and policy makers alike to develop tailored and targeted lifecourse interventions so that transport-related physical activity may be integrated into everyday life.