Most children run slower than their parents did at the same age.

Not being as fit in childhood can lead to health problems down the road, an American Heart Association news release reported via EIN Newsdesk.

"If a young person is generally unfit now, then they are more likely to develop conditions like heart disease later in life," Grant Tomkinson, Ph.D., lead author of the study and senior lecturer in the University of South Australia's School of Health Sciences, said.

"Young people can be fit in different ways. They can be strong like a weightlifter, or flexible like a gymnast, or skillful like a tennis player. But not all of these types of fitness relate well to health. The most important type of fitness for good health is cardiovascular fitness, which is the ability to exercise vigorously for a long time, like running multiple laps around an oval track," he said.

Researchers looked at data from 50 studies that took place between 1964 and 2010 that encompassed over 25 million kids between the ages of nine and 17 in 28 countries. They looked at both how long children could run for, and how long it took them to complete a course. The tests included in the study lasted for between five and 15 minutes and covered no more than two miles.

The team found that physical endurance "declined significantly" over the course of the 46 year study. The changes were similar regardless of gender or age, but did vary according to country.

The study determined children's endurance dropped by sic percent in the U.S. between the years of 1970 and 2000. Globally, endurance has dropped by five percent.

On average, children were found to be 15 percent less fit than their parents were at the same age and kids run a mile about one minute slower than children 30 years ago.

"We need to help to inspire children and youth to develop fitness habits that will keep them healthy now and into the future," Tomkinson said. "They need to choose a range of physical activities  they like or think they might like to try, and they need to get moving."