Children are now slower runners than their parents were, according to new data from the American Heart Association.
The study showed that around the world, children are 15 percent less fit than their parents were during childhood. In the United States, childhood cardiovascular performance declined between 1970 and 2000.
On average, it takes children 90 seconds longer to run a mile than their counterparts did 30 years ago. Heart-related fitness has declined 5 percent per decade since 1975 for children ages 9 to 17.
Health experts recommend that children 6 and older get 60 minutes of moderately vigorous activity accumulated over a day. Only one-third of American kids do now.
NPR pulled together some of the main reasons for slipping childhood physical activity:
• Increased weight explains 30 to 70 percent of the declines in children's aerobic fitness, according to Grant Tomkinson , an exercise physiologist who led the study.
• Higher body mass index "may contribute to the decrease in the running performance of late-teenage girls observed recently," Japanese scientists wrote in 1998, in one of the studies used.
• Lower levels of physical activity, both in organized sports and at play, account for a lot of the rest, they say.
The recent study continues to sound alarm bells regarding childhood health. How does this new research fit into the big picture? What are the long term effects on society if declining fitness levels in children persist?
The Associated Press contributed to this report.