NEW YORK (Reuters Health) - Today's overachieving kids are starting sports earlier and training longer and harder, often before they enter Kindergarten, and many of them are suffering overuse injuries as a result, according to Dr. Lyle Micheli.

Micheli is director and co-founder of the world's first sports medicine clinic for children located at Children's Hospital Boston.

"Overuse injuries result from overtraining," Micheli said. "Certainly, as the volume of training increases, the risk of injury increases." Twenty years ago, he noted in an interview with Reuters Health, "we didn't see overuse injuries in kids, but today we do."

Micheli said he sees about 300 kids each week in his sports medicine clinic and "60 to 70 percent of the injuries are overuse injuries. Twenty-years ago, it was quite the opposite. It was mostly acute injuries, not overuse injuries."

Children who participate in individual sports like gymnastics, tennis, and swimming, where they typically put in more hours of training, are particularly at risk, Micheli said. For children in these sports, "we see stress fractures and even tendonitis, which is unusual in children."

Young baseball pitchers with injuries to their pitching arm are also seen. "Today's young pitchers are throwing harder and earlier and some may 'just play through it' when the arm is sore, which makes it worse and may lead to permanent damage," Micheli warned.

He urges parents and coaches to be sensitive to changes in performance and attitude in young athletes -- changes that may signal overtraining and burn out and may come before the actual physical injury.

Often a young athlete will push himself or herself to train harder and longer for the coach. "To a 10-year-old, their coach is God," Micheli noted.

Micheli thinks it's time for "mandatory safety education and maybe even certification" for coaches of school-age children. "We have a whole cadre of well-meaning volunteer coaches out there and they have variable levels of knowledge including the sports they are dealing with," he said.

"If we were to do one thing to have an impact and improve the safety of kids' sports," Micheli said, "it would be coaching education and certification. Some sports are moving toward this, like soccer, where in some places you can coach for one year and after that you have to take the coaching course."