Background: It has been evident that there is a sharp decline in participation in physical activity for adolescent girls. Using social cognitive theory as a theoretical framework, this study was designed to examine the relationships between several psychosocial constructs and physical activity levels in adolescent girls, as well as their differences across several ethnicities. 

Methods: Participants were 92 sixth through ninth grade girls recruited from four urban schools. All girls’ psychosocial correlates (self-efficacy, outcome expectancy, and social support) were measured and used to predict their physical activity levels as measured by W4L Neo II pedometers (mean steps per day and mean time spent in Moderate to Vigorous Physical Activity [MVPA]).  

Results: Girls’ self-efficacy emerged as the sole predictor of their mean steps (β = .36, p < .01) and mean time in MVPA (β = .38, p < .01). However, girls’ outcome expectancy and social support failed to predict physical activity levels. Additionally, White girls had more daily steps and daily physical activity time than the AfricanAmerican girls did.  

Conclusion: Adolescent girls’ self-efficacy appeared as the only predictor of their daily physical activity levels,  and therefore interventions to enhance their self-efficacy should be considered.