KANSAS CITY, Mo. — Anyone who's ever coached a young athlete recognizes the feeling — when pride and admiration turn to frustration or impatience when a shot is missed or a ball is dropped.

Countless times each year, coaches from kindergarten to college are able to turn those feelings into teachable moments and encouragement, approaches that almost always lead to better player or team performance.

But sometimes a darker side emerges: A player is yelled at, severely punished, even physically abused.

It's not clear what happened last week with University of Kansas head football coach Mark Mangino, who is facing allegations of abuse. An investigation is under way following complaints by players and parents.

Yet the problem of overly aggressive youth coaching is growing in America. Indeed, three out of four young players quit organized sports before the age of 13, according to one survey, blaming overly aggressive coaching more than any other reason.

"The win-at-all-costs mentality that's filtered down from professional sports has colored youth sports," said Jim Thompson, founder of a California-based organization called the Positive Coaching Alliance, which counsels coaches at the high school level and below. "Youth coaches are imagining in their heads that they're an NBA coach or an NFL coach."

A survey by the Citizenship Through Sports Alliance gave youth coaching a C grade in 2005, calling the lack of focus on effort, skill development, positive reinforcement and fun "unacceptable."

"Youth sports has lost its child-centered focus, meaning less emphasis on the child's experience and more emphasis on adult-centered motives, such as winning," the group concluded.

Of course, the use of what might politely be called intense verbal encouragement has long been a part of organized athletics. Most men or women who've ever played a game can tell stories of a coach who raised his or her voice in an effort to improve concentration and execution on the field or court.

But a growing body of study suggests the in-your-face approach to coaching can be counterproductive for some players.

"If you're going to jump on a kid and berate them verbally, they're going to shut you off," said Tim Grunhard, an NFL veteran now coaching at Bishop Miege High School in Shawnee Mission, Kan. "That's something as a coach you have to adapt to."

Grunhard, who was surprised by the allegations involving Mangino, said college coaches from Joe Paterno at Penn State to Pete Carroll at Southern California have either abandoned the military "boot camp" model of football coaching or never engaged in it at all.

In fact, organizations providing guidance to youth coaches have made a less-aggressive coaching technique a centerpiece of their recommendations for those who lead athletic teams.

The National Alliance for Youth Sports, which conducts training seminars for amateur youth coaches across the country, has even published a code of ethics. It requires adherents to "place the emotional and physical well being of my players ahead of a personal desire to win. "

Most parents would agree with those goals. But coaches argue — perhaps with some justification — that parents also want their children's teams to win, especially after investing hours of time and hundreds of dollars to improve performance.

That can increase pressure on coaches, who can sometimes turn up the heat on athletes.

But what might not be acceptable in a middle-school weekend football league might be tolerated for a while in Division I football. After all, millions of dollars are at stake in major college sports such as football and basketball.

"When you get to the college level, there's a lot more stress on a coach," Grunhard acknowledged. "But you have to treat your players with respect if you want your players to respect you, and I think sometimes coaches blur that line a little bit."

"It's not a good thing for society having a bunch of kids doing what they're doing because they're being browbeaten by their coaches," Thompson said.