An SDT-informed online intervention supporting children's home-based exercise: A randomized controlled trial

This randomized controlled trial evaluated the effectiveness of a Self-Determination Theory (SDT)-informed online intervention in promoting moderate-to-vigorous physical activity (MVPA) among Hong Kong primary school students. Over two academic years (2022 - 24), 119 child-guardian dyads were randomly assigned to: (1) Exercise Only, (2) Coaching Only, (3) Exercise-plus-Coaching, and (4) a Waitlist Control. For eight weeks, guardians accessed private Facebook groups, receiving either exercise videos, SDT-informed coaching cues, or both. MVPA (ActiGraph) and motivation (SDT scales) were assessed at Baseline (T1), Post-intervention (T2), and Follow-up (T3). Significant group × time interaction effects indicated that both Exercise Only and Exercise-plus-Coaching groups showed increases in MVPA from T1 to T2 (small to medium effect sizes). However, these gains diminished by T3. Similarly, intrinsic motivation and identified regulation were better maintained in the intervention groups with coaching cues, whereas the Waitlist Control showed declines by T2 and T3. Improvements in autonomy and relatedness satisfaction occurred only in the groups involving exercise videos. Findings demonstrated the short-term efficacy of guardian-led, SDT-informed digital interventions in buffering declines in physical activity and motivation. The value of autonomy-supportive environments and parental involvement is underscored as facilitators of acute engagement. This research contributes to the evidence base supporting the potential for digital dissemination while acknowledging the structured support required for effective delivery. Future research should explore more intensive intervention protocols and investigate how the social connectivity and motivational features of platforms like Facebook can enhance long-term maintenance and broader accessibility across diverse populations.