That's according to a study published in the American Journal of Sports Medicine in June.
The authors looked at 302 high school athletes who were put into categories based on the number of sports they played. They found that athletes considered highly specialized were more than twice as likely than the others to report a history of overuse knee and hip injuries. The risk was especially great among those who participated in a single sport for more than eight months of the year.
While the study was in a relatively small and specific group, the results square with scientists' general understanding of appropriate training levels for young athletes.
Eric Post, research assistant at the Wisconsin Injury Sports Lab and coauthor of the study, got involved in this research when he noticed an increased trend in youth sports towards early specialization.
Current recommendations state that youth athletes should not participate in a single organized sport for more than eight months out of the year and should not participate in more hours per week of organized sport than their age (i.e., a 13 year old should not participate in more than 13 hours per week of organized sport).
Yet when the researchers surveyed parents, they found that most of them were not aware of the recommendations against overtraining and over-specialization in kids, though about half "thought that early specialization was a problem in youth sports and 76% ... were concerned about the risk of injury," Post told Business Insider in an email.
"Clearly," he wrote, "more work is needed ... in order to educate parents regarding recommendations for safe youth sport participation."
Andre Penner/AP
What about Olympians?
Post also had some thoughts on how this relates to the Olympics, and anyone aspiring to make it to that level someday.
"I think it's important to remember that the athletes competing at the Games are the top 0.1% of the 1% in terms of the athletic population," said Post. "There's a prevailing thought that as long as your child gets 10,000 hours of practice they will become an expert in that sport, but this seriously downplays the effects of genetics and environment on elite sport performance and this thought can lead to intense, year-round participation at early ages."
The research shows that highly specialized training at a young age is associated with overuse injury and psychological burnout, especially when the decision to specialize is parent-driven and not child-driven.
Post noted that, in fact, various studies have shown that elite and Olympic-level athletes actually specialized in their sport at a later age than non-elite athletes (outside of certain sports such as gymnastics or figure skating). These findings reinforce the idea that there are multiple pathways to success and that early specialization is not a guarantee of future sporting achievement - and may even hurt a kid's future chances.
"If a child decides they want to dedicate themselves completely to one sport," Post explained, "this can be most safely accomplished by providing adequate rest (at least 3-4 months of rest or cross-training during the year) and a gradual and progressive increase in [hours of training] throughout the sport season."