There is a widely held and influential view that physical activity begins to decline at adolescence. This study aimed to identify the timing of changes in physical activity during childhood and adolescence.
John Reilly from the University of Strathclyde, Glasgow, in Scotland research study found that sedentary behaviors begin to set in shortly after the ripe old age of 7.
Longitudinal cohort study (Gateshead Millennium Study) with eight years of follow-up, from Northeast England. Cohort members comprise a socioeconomically representative sample studied at ages 7, 9, 12 and 15 years; 545 individuals provided physical activity data at two or more time points.
Habitual total volume of physical activity and moderate-to-vigorous intensity physical activity (MVPA) were quantified objectively using the Actigraph accelerometer over 5-7 days at the four time points. Linear mixed models identified the timing of changes in physical activity across the 8 year period, and trajectory analysis was used to identify sub-groups with distinct patterns of age-related changes.
Four trajectories of change in total volume of physical activity were identified representing 100% of all participants: all trajectories declined from age 7. There was no evidence that physical activity decline began at adolescence, or that adolescent declines in physical activity were substantially greater than the declines during childhood, or greater in girls than boys. One group (19% of boys) had relatively high MVPA which remained stable between ages 7-15 years.
Overall, the investigators found that physical activity levels among the kids started falling at the age of 7. The declines continued during the study, but did not drop more sharply once they hit adolescence.
Most of the boys (61 percent) were moderately active when the study began, but this activity level gradually declined over the course of the eight years, the findings showed.
Among the girls, 62 percent had moderate activity levels that fell gradually throughout the study — just like the boys, according to the report.
The results were published online March 13 in the British Journal of Sports Medicine.
Reilly’s team pointed out that the results don’t prove a cause-and-effect relationship. But the findings could help shape public policy on how to help keep young people active as they grow up, the authors suggested in a journal news release.
Future policy and research efforts to promote physical activity should begin well before adolescence, and should include both boys and girls.
Study was conducted by;
Kathryn N Parkinson
Ashley J Adamson
Mark S Pearce
Jessica K Reilly
Adrienne R Hughes
John J Reilly