Secular trends in physical activity in adolescents: A systematic review.

Objective: One in five adolescents has been estimated to perform sufficient physical activity (PA), thus potentially indicating that PA among adolescents has declined. This systematic review was aimed at reporting and summarizing the available knowledge regarding PA secular trends in adolescents over time.

Methods: Seven databases were consulted (Web of Science, Scopus/Elsevier, Medline/PubMed, ScienceDirect, Lilacs, Physical Education Index, and SPORTDiscus), and 1809 studies were examined.