obesity and physical inactivity are on the rise amongst canadians. dog sports, agility in particular, may represent a form of physical activity that can help address the health issues that some of our population face. however, some individuals elect to participate in the sport less frequently while others engage in very high amounts of agility. because increased participation in physical activity is good for health, an understanding of why some individuals engage in agility in high amounts needs to be developed. the study utilized the self-determination theory (sdt) to investigate social/ environmental factors that influence the motivational sequence amongst adult agility participants to understand why some individuals engage in high amounts of the sport. meeting the recommended amounts of physical activity is linked to improved health, so an exploration into how much physical activity is achieved through agility participation was also completed. finally, the tenets of the sdt were utilized to assess how motivation influences physical activity behaviours. method: the study utilized a cross sectional mixed methods design that involved two components., competitive adult agility participants were assessed (n=233) in component one. participants filled out the sms ii, the bnsss, a physical activity inventory, and a demographic questionnaire. t and mann-whitney u tests were used to identify differences in motivation and hierarchal regression analysis was used to predict physical activity behaviours from the tenets of the sdt. seven individuals who participated in component one and engaged in higher amounts of agility participation were then interviewed for component two regarding the social/environmental factors that influenced their agility involvement. results: those who engage in higher amounts of agility had significantly higher levels of intrinsic motivation (u(231)=3321.5, z=-3.178, p<.001). on average, the sample expended 700kcal/week through their agility participation, effectively accruing 70% of the recommended amount of physical activity. self-determined motivation was able to positively predict the amount of agility related energy expenditure, and the overall frequency of agility participation. interviews in component two revealed ten social/environmental factors that influenced motivation, including: task/ego orientation, dog influence, family, friends, mentors, initial success, interspecies bond, challenge, and the venue. conclusion: the findings revealed that, in this context, agility competitors experience high levels of self-determined motivation and need satisfaction, and those with higher intrinsic motivation tend to participate more. social/environmental factors in the sport of agility may influence the motivational sequence and how much individuals participate. the present study provides a backbone for more experimental exploration to determine the relationships between the motivational sequence constructs and how they directly impact physical activity behaviours.