No studies have been published to confirm this phenomenon. But many trainers and orthopedists say the anecdotal evidence is jarring, and medical staffs for Major League Baseball teams and franchises in other sports are scrambling to understand why athletes’ hips suddenly seem so fragile.

Experts said other factors could be at work in addition to the overemphasis on leg strength. Advances in magnetic imaging have enabled doctors to see inside the hip and identify certain ailments, and the increasing number of children playing sports at younger ages has led to more instances of improper bone development.

Several of baseball’s biggest stars  including Alex Rodriguez of the Yankees, Chase Utley of the Philadelphia Phillies and Carlos Delgado of the Mets  have been forced to the sideline after having surgery to repair a torn labrum, the cartilage that runs along the rim of the hip socket. Rodriguez recently returned after missing two months, and Delgado has said he may not return this season. On Thursday, one of Utley’s teammates, pitcher Brett Myers, was found to have a damaged labrum in his hip. He is expected to have surgery this week.

Not all doctors are convinced that training is the culprit.

“It’s not like workouts have changed all of a sudden; it doesn’t explain it,” said Christopher Powers, an associate professor of biokinesiology at the University of Southern California. “People and doctors are just more aware of it diagnostically. We’ve always had hip problems; now we are just finding it better.”

The number of players on the disabled list because of hip and groin-muscle injuries rose to 34 in 2008 from 20 in 2007. Through the first quarter of this season, at least 13 players have gone on the disabled list with hip injuries.