Getting children to move more at home — without a gym, a coach, or a school PE class — remains one of the hardest problems in pediatric health promotion. A randomized controlled trial testing a guardian-delivered, Facebook-based exercise program offers a nuanced look at what works short-term and why sustainability remains elusive.
The trial enrolled 119 child-guardian pairs across two Hong Kong academic years (2022–2024), distributing them across four conditions: exercise videos only, Self-Determination Theory (SDT)-informed coaching cues only, a combined condition, and a waitlist control. Over eight weeks, guardians administered the intervention via private Facebook groups. Moderate-to-vigorous physical activity was objectively measured via ActiGraph accelerometry at baseline, post-intervention, and follow-up. Both the exercise-video-only and the combined exercise-plus-coaching groups produced significant MVPA gains from baseline to post-intervention, with effect sizes in the small-to-medium range. Critically, intrinsic motivation and identified regulation — two higher-quality motivational forms in SDT's taxonomy — showed better maintenance in groups that received coaching cues. Yet by follow-up, physical activity gains had largely receded across all active arms.
This study sits within a growing literature confirming that digitally mediated, parent-involved interventions can spark short-term behavior change in children, but the fade-out problem is not new. What adds nuance here is the motivational decomposition: coaching cues preserved autonomous motivation even when activity levels slipped, suggesting that psychological scaffolding and behavioral outcomes may decouple over time. The reliance on Facebook as a delivery platform introduces engagement variability and potential selection bias among more digitally active families. The sample of 119 dyads, while adequate for detecting medium effects, limits generalizability across cultural and socioeconomic contexts beyond Hong Kong. This trial is best characterized as confirmatory of SDT's short-term applicability in digital pediatric settings — incremental rather than paradigm-shifting — and underscores the urgent need for studies exceeding 12 weeks to identify maintenance strategies.