Declining Outdoor Recreation and Increased Use of Fitness Centers Among Norwegian Adolescents, 2010-2019.

Adolescents' physical activity patterns appear to be changing, with indications of a shift from nature-based activities toward more structured, indoor forms of exercise. However, it remains unclear how participation in outdoor recreation and fitness center use has developed in parallel over time, and whether these trends vary by degree of urbanization. The aim of the present study was to examine the trends in adolescents' engagement in outdoor recreation and use of fitness centers across Norwegian municipalities between 2010 and 2019 and to assess how these patterns relate to individual and contextual factors. Repeated cross-sectional data were drawn from the Ungdata survey (N = 67,554), and multilevel linear models were applied to estimate time trends and test interactions with municipal population density. Analyses were adjusted for depressive symptoms, gender, school grade, and vegetation density (NDVI). The results indicated a significant decline in outdoor recreation during the period, particularly in more urban municipalities, alongside a marked increase in fitness center use. The two activity types were positively associated but not mutually exclusive. The findings point to a broader shift in adolescent activity preferences that may reflect changing environmental and sociocultural conditions. These patterns underline the need for public health approaches that recognize diverse forms of youth engagement in physical activity.