Physical activity levels among teenagers are similar to that of 60-year olds, according to US research.

The study confirmed that World Health Organization (WHO) recommendations of at least 60 minutes of moderate-to-vigorous physical activity a day for children aged five to 17 years were not being met.

Johns Hopkins Bloomberg School of Public Health researchers in Baltimore, Maryland, used data from the National Health and Nutrition Examination Survey in 2003-2004 and 2005-2006. They analysed the data of 12,529 participants who wore tracking devices for seven straight days, removing them when taking a bath or at bedtime. The devices measured how much time participants were sedentary or engaged in light or moderate-to-vigorous physical activity.

Findings were broken down into five age groups: children (ages six to 11); adolescents (ages 12 to 19); young adults (ages 20 to 29); adults at midlife (ages 31 to 59); and older adults (age 60 to 84). Forty-nine percent were male and 51 per cent were female.

More than 25 percent of boys and 50 percent of girls aged six to 11 and more than 50 percent of male and 75 percent of female adolescents aged 12 to 19 did not meet the WHO recommendation.

The findings, published in the journal Preventive Medicine, showed that 20-somethings were the only group that saw an increase in activity levels, with exercise spread out throughout the day.

For all age groups, males generally had higher activity levels than females, particularly high-intensity exercise, but after midlife, these levels dropped off sharply compared to females. Among adults 60 years and older, males were more sedentary and had lower light-intensity activity levels than females.

The study’s senior author, Vadim Zipunnikov, assistant professor in the Bloomberg School’s Department of Biostatistics, said: “Activity levels at the end of adolescence were alarmingly low, and by age 19, they were comparable to 60-year-olds. For school-age children, the primary window for activity was the afternoon between 2 and 6pm. So the big question is how do we modify daily schedules, in schools for example, to be more conducive to increasing physical activity?

“The goal of campaigns aimed at increasing physical activity has focused on increasing higher-intensity exercise. Our study suggests that these efforts should consider time of day and also focus on increasing lower-intensity physical activity and reducing inactivity.”