(Reuters Health) - Children and teens who specialize in one sport may be more likely to get injured than those who play a variety of sports, a new study suggests.

Researchers examined data from five previously published studies with a total of about 5,600 athletes age 18 or younger.

Compared to athletes who played the widest variety of sports, youth who specialized the most were 81 percent more likely to experience an overuse injury, the study found.

“Being a highly specialized athlete means that you can identify a primary sport, you train more than eight months/year for that sport, and you have quit other sports to focus on your primary sport or have only ever played your primary sport,” said study leader David Bell of the University of Wisconsin-Madison.

“Theoretically, this intensive training results in repetitive motions that result in muscle imbalances and increase injury risk,” Bell said by email.

The smaller studies in the analysis examined a wide variety of popular youth sports: soccer, basketball, tennis, volleyball, softball, football, track, cross country, wrestling, swimming, ice hockey, lacrosse, baseball, cheerleading and gymnastics.

Sports specialization was determined based either on how many sports athletes said they played or on a scale ranking the proportion of their focus on each sport they played.

Across all of the studies, about 13 percent to 38 percent of the young athletes specialized in a single sport, researchers report in Pediatrics.

The proportion of highly specialized athletes who experienced injuries ranged from about 5 percent to 28 percent across the smaller studies.

Highly specialized athletes were 18 percent more likely to have an overuse injury than moderately specialized athletes who spent at least some time on two or more different sports.

Moderately specialized athletes were also 39 percent more likely to have an overuse injury than athletes who played a wide variety of sports.

The smaller studies in the analysis weren’t controlled experiments designed to prove whether or how sports specialization might directly cause injuries. Researchers also lacked data on how much time athletes spent practicing or playing specific sports, information that can be used to help calculate injury rates based on hours of participation.

Even so, the results point to consistent findings that specialization is associated with an increased rate of overuse injuries, said Jennifer Sacheck, an exercise and nutrition researcher at George Washington University in Washington, D.C. who wasn’t involved in the study.

“We do know that overtraining and drop-out rates increase as children specialize into one sport,” Sacheck said by email. “The fact that overuse injury is indeed part of the equation is important and critical for athletes, parents and coaches to understand.”

Overuse injuries occur when muscles, tendons or ligaments experience higher stress than they are used to, said Mathieu Belanger a researcher at the University of Sherbrooke in Quebec, Canada, who wasn’t involved in the study.

“This is particularly common among youth who specialize in only one sport since they engage in frequent repetitions of the same movements over and over,” Belanger said by email. “Without a proper balance of movements, it is possible for youth, who are still in their developmental phases, to lack the equilibrium required to avoid injuries.”

While parents may encourage children to pursue a single sport and push them to train harder in hopes of a college scholarship, families need to bear in mind that fewer than 1 percent of children get these scholarships, Bell advised.

“Don’t let that be a driving factor for sports participation,” Bell said. “Make sure that your child is having fun playing sports.”

SOURCE: bit.ly/2Li6mqg Pediatrics, online August 22, 2018.