New research confirms previous findings that young children and teenagers who train intensely as single-sport athletes have a much higher risk of sustaining severe overuse injuries, like stress fractures.

"We should be cautious about intense specialization in one sport before and during adolescence," said Dr. Neeru Jayanthi, a sports medicine specialist at Loyola University Medical Center, in a news release. "Among the recommendations we can make, based on our findings, is that young athletes should not spend more hours per week in organized sports than their ages."

Jayanthi presented his findings today at the American Medical Society for Sports Medicine (AMSSM) meeting in San Diego.

The research observed 1,206 athletes ranging in age from 8 to 18, all of whom had come to the Lurie Children's Hospital of Chicago between 2010 and 2013 for physicals or treatment for sports injuries.

Each athlete was rated on a six-point sports specialization scale, which assigned one point each for factors like training more than 75 percent of their time in one sport, training more than eight months per year, and quitting other sports to focus on only one.

There were 859 injuries in the sample, 564 of which were overuse injuries like stress fractures in the back or limbs; elbow ligament injuries; and joint cartilage and bone injuries, called osteochondral injuries. Such serious injuries can keep young athletes on the bench for up to six months, and even keep them from playing competitively afterward.

The final tally of the six-point specialization scale counted scored injured athletes at an average of 3.3, while uninjured athletes scored 2.7. The young athletes who suffered injuries spent about 21 hours per week playing sports, working out, or otherwise physically active, while those with no injuries spent about three hours less.

Over 3.5 million children younger than 15 were treated for sports injuries in 2010, reports the American Academy of Orthopaedic Surgeons. Since children's musculoskeletal systems are still growing, they are especially vulnerable to injuries from overusing joints and ligaments.

In the news release, Jayanthi suggests that young athletes follow these tips to reduce their risk of overuse injuries:

  • Do not specialize in one sport before late adolescence.
  • Do not spend more hours per week than your age playing sports, since younger children are developmentally immature and are typically less able to tolerate physical stress.
  • Do not spend more than twice as much time playing organized sports as you spend in gym training and unorganized play.
  • Do not play competitive sports year round. Take a break from competition for one tothree months per year, not necessarily consecutively.
  • Take at least one day off per week from sports training.