Abstract
BACKGROUND: We aimed to investigate the effectiveness of health belief model-based nudge messaging on engagement in stretching that was either threat-based or benefit-based. METHODS: A quasi-experimental design allocated the participants (N=69) into three groups: the threat nudge group, which received messages emphasizing perceived susceptibility and severity; the benefit nudge group, which received messages on the advantages of stretching; and the control group, which received no messages. The study was conducted in South Korea from October to November 2024. Participants' engagement in stretching was measured over a six-week period using the health application, which provided the stretching exercise sessions and tracked and recorded their duration. RESULTS: The threat nudge group exhibited the largest increase in stretching behavior, significantly outperforming both the benefit nudge group and the control group. The benefit nudge group showed an improvement but it tended to be a generally smaller and less dramatic effect than the threat nudge group. Analysis of variance showed a significant difference in stretching time across groups (F (2,67) = 26.43, P=.000; η(p) (2) =0.44), with post-hoc tests indicating that the threat nudge group significantly outperformed both the benefit nudge and the control group in stretching duration. CONCLUSION: One implication of these findings was that, as suggested by the health belief model, perceived threat can be a strong motivator for behavior change in the short term while perceived benefits alone may not be sufficient to drive immediate action. Practically, threat-based messaging can be particularly useful in the short term for physical activity instructors and app developers to motivate clients.