Digital health interventions for promoting physical activity among adolescents: a systematic review.

Background: The issue of insufficient physical activity in adolescents (defined by the World Health Organization as those aged 10-19 years) is a significant worldwide health concern, as 81% do not achieve the suggested levels of physical exercise. Although digital health interventions (DHIs) present promising scalable solutions, their actual performance in practical environments often falls short of anticipated outcomes. This systematic review provides a critical analysis of the existing research on digital strategies aimed at enhancing physical activity among adolescents, emphasizing the factors that contribute to their success, user engagement, and equitable access. Methods: This systematic synthesis compiles findings from scholarly articles released from 2020 to 2026. The primary outcome was physical activity, measured by daily step counts or minutes of moderate-to-vigorous physical activity (MVPA). Secondary outcomes included engagement, adherence, motivation, psychological factors, equity, and other health-related measures. We included randomized controlled trials, cohort studies, cross-sectional studies, mixed-methods studies, systematic reviews, and meta-analyses. By examining research on a range of digital health technologies-including wearable devices (e.g., fitness trackers, smartwatches), mobile applications, gamified platforms, chatbots, and AI-driven tools-the analysis integrates quantitative data with qualitative insights from co-design studies to provide comprehensive insight into the effectiveness, timing, and target audiences of digital interventions. Methodological quality and risk of bias were assessed using study-design-specific tools: RoB 2 for randomized controlled trials, ROBINS-I for non-randomized interventional studies, AMSTAR 2 for systematic reviews and meta-analyses, NOS for cohort and longitudinal studies, AXIS for cross-sectional studies, CASP for qualitative studies, and MMAT for mixed-methods studies. Results: The results reveal a persistent disparity between effectiveness and user involvement: while 63% of the examined DHIs demonstrated positive results in their initial assessments, adherence levels dropped from 73% at the start to just 14% by the fifth month. (The 63% = 29/48 studies reporting a significant positive effect on PA. The adherence rates are from a single cohort study tracking device usage over time, not pooled across studies). The success of these interventions is not solely dependent on advanced technology but rather on the integration of three interconnected factors: (1) developmental suitability, where younger adolescents (approximately 10-13 years) are more responsive to playful, sensorimotor activities, whereas older adolescents (approximately 14-19 years) prefer goal-setting and tracking their own progress. (2) relational design, features like team challenges, empathetic AI characters, and customizable avatars can boost confidence by 50% and motivation by 120%; and (3) contextual relevance, data indicates that moderate to vigorous physical activity (MVPA) peaks between 5 and 8 p.m., highlighting the critical difference between screen time (which can hinder activity) and the frequency of physical engagement (which encourages it). Ongoing disparities in equity-such as digital literacy gaps exceeding 35% and reduced engagement among racial and ethnic minorities-emphasize the need for intentional structural and cultural alignment to prevent digital interventions from widening existing inequalities. Conclusion: Effective digital solutions prioritize the needs of adolescents rather than focusing solely on technology. They emphasize tailored experiences instead of fixed features, foster meaningful connections rather than relying on precise algorithms, and adapt to specific contexts instead of aiming for one-size-fits-all scalability. Future developments should shift away from merely measuring screen time and instead embrace approaches that are rich in experience, affirm individual identities, and promote social justice while incorporating physical activity into the everyday lives of young people. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261415756.