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Effects of a self-determination theory-based mail-mediated intervention on adults' exercise behavior
Susan S Levy1, Bradley J Cardinal
1Department of Exercise and Nutritional Sciences, San Diego State University, San Diego, California 92182-7251, USA. slevy@mail.sdsu.edu
Purpose:
To examine the effect of a mail-mediated intervention, based on self-determination theory, on adults'exercise behavior.
Methods:
The study was a randomized control trial conducted over a 2-month period. Of the initial 185 volunteer participants, 126 (68.1%) completed questionnaires at baseline, 1 month, and 2 months. Participants in intervention-only and intervention-plus-booster groups received a mail-delivered packet containing strategies designed to promote perceptions of autonomy, competence, and relatedness regarding exercise. Those in a control group received an American Heart Association physical-activity facts packet. After 1 month, those in the intervention-plus-booster group received a booster postcard, reiterating the main points of the initial intervention packet. Exercise behavior was the primary outcome variable. Perceptions of autonomy, competence, and relatedness were evaluated as mediating variables.
Results:
Separate 3 (group) x 3 (time) repeated measures analyses of variance conducted for men and women revealed that for women, all three groups significantly increased exercise levels over the 2-month period. No significant interactions were found regarding the influence of the intervention on the mediating variables. A process evaluation indicated a lack of compliance regarding completing intervention-packet worksheets.
Discussion:
Findings suggested that more intensive interventions and greater fidelity of treatment may be needed to evidence change in exercise behavior.
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