Does image congruence impact the effectiveness of a gain-framed physical activity message?

Background: Gain-framed messages can improve processing and physical activity, however inconsistency remains about the merits of using different accompanying images. This study explored whether gain-framed messages alongside positive images (congruent) were more effective than negative (incongruent) images at increasing Social Cognitive Theory (SCT) constructs and moderate-to-vigorous physical activity (MVPA). Method: Using a mixed design participants (N=110) were randomly assigned to read a gain-framed physical activity booklet containing either congruent or incongruent images. Data were collected at two time points (baseline and one week later) using online questionnaires assessing SCT constructs and interviews about MVPA over the previous seven days. Results: A time by condition interaction showed that intentions (p=.039, η2=.04) and self-efficacy (p=.005, η2=.07) increased in the congruent condition only. There was a time main effect for self-regulation (p=.001, η2=.09) and MVPA (p=.011, η2=.06), but no difference between conditions. Changes in self-regulation predicted changes in MVPA in both conditions (congruent, p=.003; incongruent, p=.030). Conclusions: Congruence between message content and images increased intentions and self-efficacy, but not MVPA. Improving self-regulation may increase physical activity levels regardless of message congruence.