ST. LOUIS, July 24 (UPI) -- For physical and emotional reasons, children need time off from sports, a researcher at Washington University School of Medicine in St. Louis said.

Dr. Mark Halstead, a pediatric sports medicine specialist at St. Louis Children's Hospital, said participation in any sport can lead to an overuse injury but if a child plays two sports at the same time that use similar movements, it magnifies the overuse effect and creates more potential for injury.

"The most common overuse injuries we see are tendinitis, stress fractures and irritation of the growth plates," Halstead said in a statement. "Any sport that a child participates in year-round, with no extended periods of time off, can lead to overuse injuries."

To keep young athletes healthy Halstead advises to:

-- Don't make children play through pain or make them feel that they can't tell you about their pain.

-- Young baseball pitchers shouldn't throw breaking balls, such as curveballs or sliders, until they're ready to shave; these pitches are stressful on the shoulder and elbow.

-- There's no big advantage to playing year-round sports or specializing in one sport until adolescence.

-- Make sure very active children get enough calcium, iron and calories in their diet.