Effects of a self-determination theory-based mail-mediated intervention on adults' exercise behavior.
OBJECTIVE
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.


CONCLUSIONS
Findings suggested that more intensive interventions and greater fidelity of treatment may be needed to evidence change in exercise behavior.
Levy
Susan S
SS
Department of Exercise and Nutritional Sciences, San Diego State University, San Diego, California 92182-7251, USA. slevy@mail.sdsu.edu
Cardinal
Bradley J
BJ
D000328:Adult; D000368:Aged; D000572:American Heart Association; D015444:Exercise; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D008875:Middle Aged; D009042:Motivation; D010174:Pamphlets; D026684:Personal Autonomy; D011177:Postal Service; D015397:Program Evaluation; D011582:Psychological Theory; D011795:Surveys and Questionnaires; D014481:United States