Understanding the relationship between sedentary behaviors (SB) and physical activity (PA) may lead to the development of effective intervention programs to promote active lifestyles. This study aimed to examine the prevalence and clustering of SB and PA among urban Portuguese adolescents.

The study comprised a total of 651 adolescents (378 girls) aged 12–14. Ecological Momentary Assessment was used to measure SB and PA, using 15minutes time intervals. To identify gender differences t-test was used. Cluster analyses were performed using the most prevalent SB and PA, separately for boys and girls.

Television (TV) viewing was the most consuming leisure time (boys 98min/day, girls 60min/day), followed by computer use (boys 43min/day, girls 22min/day), and talking with friends (boys 11min/day, girls 31min/day, P<0.001). Boys devoted significantly more time on screen-time and talking than girls (P<0.001). Boys practiced 41min/day and girls 24min/day (P<0.001) of sport activities. Based on these behaviors three cluster solutions were found both for boys and girls. Boys who spent more time watching TV and on the computer, spent less time studying, talking and doing PA (n=70). Boys who devoted more time to PA watched more TV and spent less time on the computer, studying and talking (n=56). Girls whose leisure time was dominated by talking with friends watched less TV and did less PA (n=49). The most active girls dedicated less time to studying, viewing TV, using the computer and talking with friends (n=105). Boys (n=147) and girls (n=224) who studied more spent less time watching TV, using the computer, talking with friends and doing PA.

Findings the study suggests a need for diverse behavioral targets in interventions design to reduce time devoted to sedentary behaviors and increasing physical activity in sub groups of adolescents.