From an article of the same title on BBCNews.com:

A team from Canada's University of Alberta compared a 10,000-step exercise programme with a more traditional fitness regime of moderate intensity.

Researchers found improvements in fitness levels were significantly higher in the second group.

They told an American College of Sports Medicine meeting that gentle exercise was not enough to get fit...

"You've got to do more than light exercise and move towards the inclusion of regular moderate activity, and don't be shy to interject an occasional period of time at the vigorous level."

From The Week, September 22, 2006 p. 21:

The epidemic of autism may be the result of men fathering children later in life, says a new study of more than 130,000 children. The number of kids with autism—a brain disorder that makes it difficult to relate to people and the outside world—has jumped tenfold in the last two decades, now affecting one in every 166 American children. Many parents blame the mercury once used as a preservative in infant vaccinations, though several studies have found no link between vaccinations and autism. But now, says New Scientist, an extensive new Israeli study has come up with a solid reason for the disorder's prevalence: older fathers. A research team that included scientists from Mount Sinai School of Medicine in New York found that a new dad between 30 and 39 was 1.6 times more likely to have an autistic child than a man of 29 or younger. Children conceived by dads between 40 and 49 were 5.75 times as likely to develop the disorder. This suggests that as men age, their sperm is more prone to developing warped genetic material. The age of the mother did not appear to have a large effect. The study, said University of Illinois autism researcher Dr. Edwin Cook, may go a long way to explaining the recent surge in autism. "It's a strong effect in a carefully designed study," Cook said.