Combining self-affirmation and implementation intentions: evidence of detrimental effects on behavioral outcomes

BACKGROUND There is limited evidence that self-affirmation manipulations can promote health behavior change. PURPOSE The purpose of this study was to explore whether the efficacy of a self-affirmation manipulation at promoting exercise could be enhanced by an implementation intention intervention. METHODS Participants (Study 1?N?=?120, Study 2?N?=?116) were allocated to one of four conditions resulting from the two (self-affirmation manipulation: no affirmation, affirmation) by two (implementation intention manipulation: no implementation intention, implementation intention) experimental design. Exercise behavior was assessed 1 week post-intervention. RESULTS Contrary to prediction, those participants receiving both manipulations were significantly less likely to increase the amount they exercised compared to those receiving only the self-affirmation manipulation. CONCLUSION Incorporating an implementation intention manipulation alongside a self-affirmation manipulation had a detrimental effect on exercise behavior; participants receiving both manipulations exercised significantly less in the week following the intervention.