Study finds teens don't need as much daily exercise as you'd think to stay healthy

MIAMI – A new study is revealing how much exercise teenagers need every day to stay healthy – and it may not be as much as you think.

Thirteen-year-old Kitty Barulis is doing a health check, completing a non-stop series of 20-yard shuttle runs. 

"It was hot, but bearable," she says.

That's exactly how researchers at University of Oxford say it should feel.  Their new study reveals children benefit from spending 20 minutes a day breathing hard and getting red in the face.

PhD student Sam Burden, from Oxford Brookes University, helped with research. 

"We really do recommend that children and adolescents get into these good habits of exercising frequently at these high levels now."

Researchers tested activity levels of more than 300 kids and found short bursts of panting and sweating were enough to improve physical, mental and cognitive health.

While the World Health Organization says children should get 60 minutes of moderate to strenuous exercise a day, Oxford's lead author, Dr. Alex Jones, found less is more if you go harder.

"You do need to get hot and sweaty - you do need to get breathless but you don't have to do it for an hour - you only have to do it for 20 minutes a day in total."

The study showed fitness benefits of grueling workouts plateau at about 20 minutes.  Researchers encourage kids to find an activity they love. 

Kitty says, "I think when you do it together you can also like motivate each other so and you wanna do well with your friends."

Kids helping kids become healthy adults.

Researchers also found that teenaged boys tend to get more vigorous exercise than girls. The findings are published in this month's Pediatrics journal.