The lack of diversified activity may not allow young athletes to develop the appropriate neuromuscular skills that are effective in injury prevention and does not allow for the necessary rest from repetitive use of the same segments in the body. The positive transfer of skill with diversification is important in the successful development of a young athlete.15,28 Until recently, we did not have enough evidence to support the concept of sports specialization as an independent risk factor for injury, apart from exposure or the combination of high volume and intensity; however, the following theories may provide some additional rationale for these risks.
Specialized Athletes Are More Likely to Have Year-Round Exposure to a Single Sport
Year-round exposure to a single sport may be one of the primary reasons for injury risk in specialized athletes. In youth baseball pitchers, there was a greater risk for shoulder and elbow surgery in those that pitched greater than 8 months per year and in those that pitched regularly with arm pain or fatigue.53 Another study of high school athletes found that athletes who did not take at least 1 sport season off during the year (eg, fall, winter, spring, or summer) were more likely to sustain an injury independent of whether the athlete was characterized as a single or multisport athlete.45 However, the lack of difference in risks between the 2 groups may be due to the fact that the weekly exposure hours were not monitored. Thus, it makes it more difficult to draw firm conclusions with regard to the risk of injury when exposure is already reduced. The risk of injury or medical withdrawal was not demonstrated in a population of 519 Midwest junior tennis players when using a similar model.38 This might be due to the very high rates of year-round training (93.4% at >9 months per year) that limited
the ability for a comparison with a control group.