Within Self-Determination Theory (Deci & Ryan, 2002) the satisfaction of competence, autonomy, and relatedness needs are thought to directly predict psychological well-being and behavioural outcomes (Deci & Ryan, 2000). The purpose of this program of research was to examine the role of psychological need satisfaction in association with psychological well-being and physical activity in participants drawn from the general population. Study 1 examined aspects of score validity and reliability for an instrument modified to assess psychological need satisfaction in physical activity contexts. Results of this investigation supported the merit of the modified instrument for use in the general population. Study 2 supported a sequence based on 3 mini-theories within SDT wherein changes in relative intrinsic goals → changes in motivation → psychological need satisfaction → changes in well-being and physical activity behaviour over 6 months. Examination of the indirect effects highlighted the role of psychological need satisfaction as potential mediators within this sequence of SDT. Next, a randomized controlled trial was conducted to examine the effect of a best possible physical activity self writing intervention on outcomes such as psychological need satisfaction, exercise self-schema, well-being, and physical activity behaviour. Study 3 was conducted using baseline data from the intervention to examine the indirect effect of psychological need satisfaction in the relationship between exercise self-schema and well-being/physical activity. Results from study 3 suggested that satisfaction of all 3 psychological needs mediated the link between descriptive exercise self-schema and well-being and that competence produced an indirect effect between descriptive exercise self-schema and physical activity. Results from the intervention investigation (study 4) revealed that a once a week writing intervention over 4 weeks increased participants’ positive affect at post-test relative to the control group; however, the intervention was largely unsuccessful at increasing psychological need satisfaction, exercise self-schema, well-being and physical activity across post-test and 1-month follow-up. Taken together, the results from the four studies in this program of research highlight the salience of psychological need satisfaction in physical activity contexts and their potential mediational role between antecedents such as goals, motivation, and self-schema and consequences such as well-being and physical activity.Education, Faculty ofKinesiology, School ofGraduat
