No activity is more familiar to children than running: running on the playground, down the street, in races or though the house. But kids today may not run like they once did.
A recent study found that the cardiovascular fitness of children and teens has declined over nearly 50 years.
This decline was seen in a decrease in children's average running speeds during long-distance running.
The authors of this study wrote that many different factors have probably contributed to the decline in kids' fitness.
The trick now is finding ways to reverse the trend.
This study, led by Grant Tomkinson, PhD, a senior lecturer in the University of South Australia's School of Health Sciences, looked at the quality of children's cardiovascular fitness across the world.
The researchers assessed this question by using existing scientific studies and focusing on changes in children's time on long-distance running exercises.
These researchers looked for all studies up through January 2013 that reported on changes in the long-distance running performance of kids aged 9 to 17, based on their times.
The findings of the 50 studies they identified were categorized based on the different countries, age and sex of the participants.
When combined, the participants across these 50 studies included more than 25 million children and teens from 28 countries, ranging from studies in 1964 through 2010.
The researchers found a substantial statistical drop in the average running speeds of children during long-distance running.
This drop was not expressed in the form of time but in how the overall average times of the kids had shifted.
In other words, the range of average times for children shifted several times in the longer direction over that time period.
The drop in average times was similar for boys and girls, for younger children and for teens and in different geographical regions of the world. There were some variations from one country to another.
"There is overwhelming evidence for substantial global declines in cardiovascular endurance performance of children and youth in recent decades," the authors of this study wrote.
"Time-related declines in cardiovascular endurance performance are probably caused by a network of social, behavioral, physical, psychosocial and physiological factors," they wrote.
The authors suggested that public health strategies need to be developed that are aimed at improving children's cardiovascular fitness.
This study was presented November 19 at the American Heart Association's Scientific Sessions 2013.
Because the study was presented at a conference and has not yet been published in a peer-reviewed journal, its findings should be interpreted cautiously.
The authors declared no conflicts of interest. No information was available regarding the study's funding.