JMIR Publications

ABSTRACT

Background:

Traditional mobile health (mHealth) interventions for physical activity (PA) primarily rely on reflective self-regulatory processes, often neglecting the role of affective associations in sustaining long-term engagement. The WalkToJoy intervention addresses this gap by applying the Affective–Reflective Theory (ART) to enhance intrinsic motivation for PA among adults 40 and older through affective message framing, evaluative conditioning, and belief updating.

Objective:

This proof-of-concept study evaluated the feasibility of the message-based WalkToJoy intervention package and examined the impact of its three components—walking suggestion prompts, salience messages, and planning prompts—on affective and behavioral outcomes related to walking.

Methods:

We conducted a 6-week full factorial experiment with an embedded micro-randomized trial (MRT) involving 49 adults aged 40 and older. Statistical analyses, including paired t-tests and generalized estimating equations (GEE), assessed pre-post changes and the effects of smile-inducing walking suggestion prompts with short, animated images in Graphics Interchange Format (GIF), salience messages, and planning prompts on weekly affective measures and daily step counts. Additionally, MRT analyses evaluated the proximal effects of these components. Post-study interviews were thematically analyzed to contextualize participants’ experiences and engagement with the intervention.

Results:

Significant pre-post improvements were observed across affective outcomes on a 7-point Likert scale: affective attitude increased by 0.547 points (p = .0002), affective valuation by 0.718 points (p = .00001), affective reflection by 0.692 points (p = .00028), and anticipated affect by 0.692 points (p = .000079). While the average daily steps showed a nonsignificant increase of 80 steps (p = .79), further analysis revealed a significant increase of 506 steps (p = .07) at the 10% significance level when comparing baseline to the average of weeks 4–6. Among the intervention components, GIF prompts significantly increased anticipated affect by 0.345 points (p = .046) and average daily step count by 1,834 steps (p = .05) compared to identical text-only prompts, supporting the effectiveness of evaluative conditioning. However, MRT analysis found no significant increase in 4-hour step counts following the walking suggestion prompts (p = .55), which was explained by qualitative findings suggesting that participants interpreted messages as flexible, day-long reminders rather than immediate calls to action. Salience and planning prompts did not yield statistically significant effects but were positively received by participants for promoting mindfulness and personalized engagement.

Conclusions:

The WalkToJoy intervention is a feasible and promising approach for increasing affective associations with walking. Walking suggestion prompts were particularly effective in boosting engagement and mitigating message fatigue, highlighting the potential of affect-driven interventions to enhance PA motivation and adherence.