[Promoting physical activity through digital technologies: everyday physical activity and mental health]

Physical activity is essential for physical and mental health. Yet intentions to be active often do not translate into action in everyday life. Habits, situational influences and momentary experiences may contribute to this gap between intention and behaviour. Digital technologies can capture these factors and physical activity in daily life and support tailored interventions.This narrative review first outlines models of reflective and automatic influences on physical activity. It then introduces ambulatory assessment for repeatedly measuring physical activity and psychological experiences in daily life and wearables for passive data collection. Just-in-time adaptive interventions (JITAIs), which can provide activity prompts at suitable moments, are also described. Two research projects on addiction and depression illustrate how these prompts might encourage physical activity and influence clinically relevant features such as craving, subjective energy or drive. Digital health applications (DiGA) are discussed as a potential route into routine care.Digital physical activity promotion offers timely and individualized support. Limitations include measurement accuracy, data quality, sustained use and the limited role of dedicated physical activity promotion in digital applications for mental disorders. Blended care approaches, in which digital tools complement face-to-face treatment in everyday life, offer potential.