Abstract
It is widely accepted that physical activity leads to health benefits. It is less well known that being frequently active leads to health benefits over and above those gained by being active a total number of minutes a week. The inclusion of frequency in research and public policy has been inconsistent and even the World Health Organisation (WHO) has recommended two different criteria for classifying an individual as ‘sufficiently active’: 1) total physical activity minutes and 2) total physical activity minutes plus frequency. To date, considerations of including frequency of physical activity is predominantly overlooked when segmenting individuals for social marketing interventions. Thus, the present study aims to examine whether frequency should be included in criteria for ‘sufficiently active’ levels of activity. Specifically, the thesis will explore whether the inclusion or exclusion of frequency when classifying individuals as ‘sufficiently active’ influences the psycho-social and physical activity levels profiles of the individuals. This thesis also aims to examine whether individuals who are active but do not meet the criteria for frequency of physical activity respond to a behavioural intervention.
For this thesis, self-reported physical activity and psycho-social data were collected from a university student sample that participated in a four-week longitudinal experiment. Using this data, four investigations evaluated whether the inclusion versus exclusion of frequency in ‘sufficiently active’ criteria could differentiate between individuals based on their 1) physical activity levels, 2) psycho-social profiles and 3) likelihood of reaching a level of physical activity associated with additional health benefits. 4) Building on the findings of the previous analyses, the fourth study in this thesis explored whether individuals who were classified as ‘sufficiently active’ using the frequency-excluded criteria would further increase their physical activity levels in response to an intervention.
Findings revealed that the inclusion or exclusion of frequency in ‘sufficiently active’ criteria led to different behavioural and psycho-social profiles of individuals classified as ‘sufficiently active’. Individuals classified as ‘sufficiently active’ using the frequency-inclusive criteria achieved higher physical activity levels and an increased likelihood of reaching a physical activity level associated with additional health benefits. They were also more likely to have psycho-social characteristics that would help their activity levels to be self-sustaining. Moreover, individuals who were classified as ‘sufficiently active’ using the frequency-excluded criteria increased their physical activity levels in response to the intervention. These findings revealed that, even though these individuals were classified as ‘sufficiently active’ using criteria that excluded frequency, they could still benefit from an intervention to increase their physical activity levels. Findings from this thesis make an original contribution to the extant research and argue clearly for the importance of frequency when classifying individuals as ‘sufficiently active’ and for the segmentation and profiling of individuals targeted in interventions or social marketing campaigns. Findings from this thesis also support the reintroduction of frequency in ‘sufficiently active’ criteria for global physical activity recommendations.