Aug. 2--Cody Lehe's life changed in a heartbeat during football practice in the fall of 2006. The senior linebacker and offensive lineman took what everybody remembers as a relatively mild hit -- a small bump to the helmet.

Seconds later, he collapsed.

"Cody grabbed another player's shoulder and fell to his knees," said Becky Lehe, Cody's mother. "Everyone thought he was joking around."

But Cody was not joking. He was lying unconscious on the field at Frontier High School, a small school in Chalmers, a White County town just north of Lafayette.

He'd suffered what doctors would later identify as "second-impact syndrome," a condition in which the brain swells rapidly after a person suffers a second concussion before symptoms from an earlier one have subsided.

Cody's first concussion was caused by a hard helmet-to-helmet hit in a game the previous weekend. For several days after the game he complained of headaches, but a brain scan indicated he could return to practice.

After his collapse at practice, he spent three months in a coma before coming home -- a shadow of what he once was.

Today, he's 21 and lives in his parents' home in Brookston. He spends most of his time in a wheelchair, though he can walk with a walker and assistance from another person. He struggles with his short-term memory.

"He'll often ask, 'How old am I?'" Becky said. "Or he'll say, 'What happened to me? How did I get this way?' That's what saddens me the most."

Cody's case underscores a serious problem in the U.S. -- too many young athletes returning to the playing field too soon after a concussion.

A new three-year study of 100 U.S. high schools found that 41 percent of concussed athletes returned to action too quickly, according to guidelines set by the American Academy of Neurology.

The guidelines say that if an athlete's concussion symptoms -- such as dizziness, headache or nausea -- last longer than 15 minutes, the player should be benched until the symptoms have been gone for a week.

The most shocking aspect of the study -- conducted by the Center for Injury Research and Policy at Nationwide Children's Hospital in Columbus, Ohio -- was the finding that 16 percent of high school football players who lost consciousness due to a concussion returned to the field the same day.