Objective: This systematic review with a three-level mixed-effects meta-analysis examined the characteristics of the programs designed to promote physical activity (PA) outdoors, seeking to identify the characteristics associated with greater health benefits, as well as the motivational strategies used to go along with the interventions. Methods: A systematic search in three electronic databases (PsycINFO, PubMed, and SCOPUS) of articles published from January 2008 to January 2020 were conducted. Two reviewers independently performed screenings, data extraction, and risk of bias (RoB) assessment of 23 studies. The meta-analysis analyzed conceptual and methodological variables that could moderate the benefits of PA in outdoor environment programs. Results: Outdoor physical activity PA-based programs have moderate effects on physical functionality and quality of life, as well as strong effects on self-concept and affectivity. A higher age and a male gender were identified in the mediation analysis as favorable conditions for the health effects. Counterintuitively, the use of motivational strategies was related to a reduction in the therapeutic benefits. Conclusions: This systematic reviews and meta-analysis analyzed the intrinsic characteristics of the programs designed to promote outdoor PA. The explicit consideration of motivational, affective or cognitive processes as possible mediating factors of adherence to participation is recommended both in the design and in the evaluation of the programs. Their great heterogeneity in the design and in the outcomes evaluated makes comparability difficult.
