If you think that teenagers are becoming weaklings, you're right.
Less than half of youths ages 12 to 15 are even close to being aerobically fit, according to data released Wednesday by the Centers for Disease Control and Prevention.
That's down from 52 percent of youths in 1999 to 2000, the last time this survey was conducted. It measures "adequate" levels of cardiorespiratory fitness, which children need not only for sports but for good health.
And that was true regardless of a child's race and family income.
Teenagers put a lot of stock in what their peers are doing, and parents are forever trying to push back against that influence. But with the advent of social media, hanging out with the wrong crowd can include not just classmates, but teenagers thousands of miles away on Instagram, Snapchat and Facebook.
When it comes to persuading teenagers not to smoke, you have to think short-term, the Food and Drug Administration says.
"While most teens understand the serious health risks associated with tobacco use, they often don't believe the long-term consequences will ever apply to them," FDA Commissioner Margaret Hamburg told reporters Monday before unveiling the agency's first-ever anti-smoking campaign.
Sure, you think, my kid's on a football team. That takes care of his exercise needs, right? Probably not.
"There are these bursts of activity," says Jim Sallis, a professor of family and preventive medicine at the University of California, San Diego. "But if you think about it, one hour of playing football out on the field means that the vast majority of that time is spent standing around waiting for the next play."