There is a prevalence of overweight children in modern American society. The major reasons for this obesity and its related negative health issues among children was noted to be correlated with an apparent sedentary lifestyle of children coupled with low physical activity levels. Children's physical activity levels were influenced not by school, family, community or students' physical activity-related self-efficacy separately, but all these factors worked together to influence children's physical activity levels according to social ecological theory.

All of the study participants were middle school girls (N = 217), with a mean age of 12 years old, and the majority were Hispanic (110, 50.7%). Fifty-nine percent of the participants were from households classified in the medium upper income range (>$50,001), with the remainder coming from lower household income levels.

The multiple factors related to influencing middle school girls' physical activity were built as a structural equation model (SEM), and then run using AMOS 15 (SPSS). The study found that (1) middle school girls' physical activity levels were low; (2) SES was a significant contributor to girls' physical activity levels by the mediating factor of self-efficacy or these girls' sedentary behavior; (3) parents' supportive attitude towards their daughter's physical activity was positively correlated with their daughter's sports team participation experience; (4) self-efficacy was negatively related to the girls' sedentary habits; and (5) girls' sedentary habits were associated with their low levels of physical activity. Implications for physical education and health intervention to increase children's physical activity levels as well as recommendations for future research are discussed.