Line up today's children against their parents at the same age in a mile race or longer and the modern child won't just lose, but, well, lose by a mile, USA Today reported. In fact, a new study out of Australia calculated the exact difference and found that today's children run a mile 90 seconds slower than their parents did 30 years ago. Overall, heart health has declined in today's youth (ages 9-17) by 5 percent per decade since 1975, according to the press release.

Conducted on a global scale, lead researcher Grant Tomkinson, an exercise physiologist from the University of Australia, analyzed over 50 studies relating to children's running fitness in 28 countries from 1965 and 2010, according to the press release. The body of research, many of which recorded how fast children ran between half a mile and two miles, covered over 25 million kids. Average changes varied according to country. The United States, for example, was slightly above the trend; heart health declined 6 percent per decade since 1975 compared to the world average of 5 percent. In China the decline was even more precipitous while in Japan today's children are nearly as healthy as the youth of yesteryear, according to USA Today.

Dr. Stephen Daniels, a Colorado pediatrician and spokesman for the heart association, wasn't surprised by Tomkinson's findings.

"It makes sense. We have kids that are less active than before," Daniels told USA Today. "Kids aren't getting enough opportunities to build up that activity over the course of the day."

One lost opportunity Daniels mentioned was recess replacing physical education classes - a common argument over the years for why children aren't getting the recommended amount of exercise per day. Health experts advise children over the age of six engage in at least 60 minutes of moderate physical activity per day. The study found that only 1 in 3 children were doing so, according to the press release.

Tomkinson specially chose to measure cardiovascular fitness and its best indicator, running.

"Young people can be fit in different ways," he said. "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."