MVPA in children/adolescents with chronic disease appear to be well below guideline recommendations , although comparable with activity levels of their healthy peers except for children with malignancies .
CONTEXT Moderate-to-vigorous physical activity ( MVPA ) and sedentary time ( ST )  are important for child and adolescent health .
OBJECTIVE To examine habitual levels of accelerometer measured MVPA and ST  in children and adolescents with chronic disease , and how these levels compare with healthy peers .
Patterns and determinants of physical activity in U.S. adolescents.
PURPOSE The objectives of this study were to describe longitudinal trends in adolescent physical activity in a sample of U.S. adolescents and to assess the effect of multiple individual , parental , and environmental factors on initial level and rates of change in adolescent physical activity . METHODS Study subjects were 12,812 boys and girls 10 to 18 years of age who were participating in the Growing Up Today Study and their mothers . We used accelerated longitudinal analysis to describe trajectories of physical activity from 1997 - 1999 , and r and om effects linear mixed models to determine which factors were independently associated with baseline physical activity and changes in physical activity over time . RESULTS Mean hours of physical activity ranged from 7.3 - 11.6 hours per week in boys and from 8.0 - 11.2 hours per week in girls . Physical activity was best modeled as a quadratic function of age , increasing until early adolescence and declining after age 13 in boys and girls . Multivariable modeling demonstrated that variables associated with physical activity level at baseline in boys and girls were age , body mass index , psychosocial variables , personal attitudes about body shape , perceived peer attitudes about body shape/fitness , parental attitudes about physical activity , parental physical activity , and environmental barriers to physical activity . Age was the only factor that predicted change in physical activity over time . CONCLUSIONS Interventions to increase physical activity in adolescents should begin before adolescence . Interventions may be more effective if they are multimodal and focus on modifiable individual , parental , and environmental factors
MVPA in children/adolescents with chronic disease appear to be well below guideline recommendations , although comparable with activity levels of their healthy peers except for children with malignancies .
CONTEXT Moderate-to-vigorous physical activity ( MVPA ) and sedentary time ( ST )  are important for child and adolescent health .
OBJECTIVE To examine habitual levels of accelerometer measured MVPA and ST  in children and adolescents with chronic disease , and how these levels compare with healthy peers .