The relative decline in MVPA affects both sexes from an early age ; however , it is greater among girls .
Moderate-to-vigorous-intensity  physical activity ( MVPA )  is important for childhood obesity prevention and treatment , yet declines with age .
Timing and magnitude of the decline in MVPA in children and adolescents are unclear but important for informing effective obesity intervention development .
This systematic review aim ed to determine and compare the year-to-year changes in MVPA among children and adolescents .
Quality of reporting of observational longitudinal research.
Observational longitudinal research is particularly useful for assessing etiology and prognosis and for providing evidence for clinical decision making . However , there are no structured reporting requirements for studies of this design to assist authors , editors , and readers . The authors developed and tested a checklist of criteria related to threats to the internal and external validity of observational longitudinal studies . The checklist criteria concerned recruitment , data collection , biases , and data analysis and descriptive issues relevant to study rationale , study population , and generalizability . Two raters independently assessed 49 r and omly selected articles describing stroke research published from 1999 to 2003 in six journals : American Journal of Epidemiology , Journal of Epidemiology and Community Health , Stroke , Annals of Neurology , Archives of Physical Medicine and Rehabilitation , and American Journal of Physical Medicine and Rehabilitation . On average , 17 of the 33 checklist criteria were reported . Criteria describing the study design were better reported than those related to internal validity . No relation was found between study type ( etiologic or prognostic ) or word count and quality of reporting . A flow diagram for summarizing participant flow through a study was developed . Editors and authors should consider using a checklist and flow diagram when reporting on observational longitudinal research
The relative decline in MVPA affects both sexes from an early age ; however , it is greater among girls .
Moderate-to-vigorous-intensity  physical activity ( MVPA )  is important for childhood obesity prevention and treatment , yet declines with age .
Timing and magnitude of the decline in MVPA in children and adolescents are unclear but important for informing effective obesity intervention development .
This systematic review aim ed to determine and compare the year-to-year changes in MVPA among children and adolescents .