For the estimated 60% of adults managing at least one chronic condition, the gap between knowing they should move more and actually doing so is a persistent clinical challenge. Adaptive digital tools that intervene precisely when and where behavior change is most achievable — rather than offering static one-size-fits-all plans — represent a meaningful shift in how health technology might support this population.
This scoping review, published in JMIR mHealth and uHealth, synthesized evidence from 14 studies examining just-in-time adaptive interventions (JITAIs) for physical activity promotion and sedentary behavior reduction in people with chronic disease. JITAIs leverage real-time data from wearables, mobile apps, and ecological momentary assessment to deliver context-sensitive prompts calibrated to an individual's current state. Among the included studies, six reported preliminary positive effects on physical activity outcomes, while three demonstrated encouraging reductions in sedentary time. The interventions drew on a range of sensor inputs and decision algorithms, though design and outcome measurement varied considerably across trials.
The findings arrive at a moment when mHealth research is grappling with a central tension: digital interventions can be highly personalized and scalable, yet their evidence base often lags behind their commercial deployment. Fourteen studies is a modest corpus — and a scoping review by design maps territory rather than quantifies effect sizes or establishes causality. Most included studies were likely small pilots or feasibility trials, making it premature to draw conclusions about long-term adherence or clinical impact. Notably, the review also catalogued engagement barriers, including notification fatigue and technical friction, which consistently undermine real-world uptake. The field would benefit substantially from larger randomized trials with standardized outcome measures. Still, the convergence of wearable sensor accuracy and machine-learning-driven decision engines is making JITAIs increasingly viable — this review provides a useful baseline map of where the science currently stands.
