Health-harnessing physical activity has been traditionally been conceptualised in terms of moderate to vigorous intensity with a recommendation to undertake 150 minutes per week of moderate to vigorous activity forms the basis for many interventions or promotion efforts. Recent advancements in the measurement of physical activity however reveals that other dimensions can incur profound health benefits such as an increase in energy expenditure or a reduction in sedentary time. Excitingly, we now have the technology to capture and present personalised visual feedback across the multiple physical activity dimensions, which could theoretically help individuals change their behaviour by providing them with more options or solutions that can be aligned to the individual’s needs, barriers and preferences. The aim of this thesis was to develop a visual presentation of multidimensional physical activity behaviour and evaluate its efficacy as a tool to support behaviour change. Firstly, a laboratory validation concluded that the BodyMedia Mini was a valid and reliable option for capturing a presenting multidimensional physical activity. Secondly, a number of visual representations were developed from minute-by-minute physical activity data captured by this monitor. Step three was to pilot these graphical depictions to group of patients and health professionals during one-to-one, semi-structured interviews who provided evidence that the design and message was clear, informative and motivating. Secondary analysis of this data suggested this was particularly true of individuals with a low physical activity status for which the personalised multidimensional feedback served to evoke strong and persuasive cognitive and emotional responses. The final steps were to test the efficacy of this approach in two multi-component, exploratory randomised controlled trials. Trial one was conducted on patients identified as at-risk (n=204) and showed that trainer led self-monitoring of multidimensional feedback had a minimal impact on behaviour. Trial two was conducted on individuals declaring themselves as inactive (n=51) and showed that using multidimensional feedback along with real-time self-monitoring appears an effective strategy for behaviour change.