When you ask why early specialization is so bad for youth athletics, people will typically refer to how it increases the risk for overuse injuries. Save for crew and the barbell sports, most sports are not exclusively bilateral. Therefore, most sports create imbalances in the body as a result of multiple unilateral movement patterns. Young athletes that suffer injuries because of specialization usually do so because they do not follow a properly periodized program.
We are moving into a generation where not only is early specialization becoming more prevalent, but also exercise in general is diminishing. Years ago, if you had a child that was playing one sport year round, he/she would still be out performing different movements at the park or playground with friends. Today, time outside of sports is spent in front of screens and using technology. Specialization in sports is taking the brunt of the criticism because it is a hot topic. In reality, it is really just the lack of various movement patterns that creates imbalances. These could be corrected however, if the athlete were to follow a properly periodized program.
Generally poor movement patterns lead to catastrophic injury when placed under load. Sports are inherently dangerous, as there is always a risk of injury, but non-contact injuries can usually be attributed to either poor movement patterns or weakness throughout a range of motion (aside from the fluky cleat getting stuck in the mud and tearing an ACL or rolling an ankle). As strength and conditioning professionals, it is our job to minimize non-contact injuries by preventing asymmetrical growth patterns.
One of the major components to overuse injuries is actually caused by suboptimal recovery, or the lack thereof all together. How often do middle and high school athletes spend time rolling and stretching? Furthermore, if they are in the gym, how often are they performing movements that are meant to aid and correct deficiencies rather than exacerbate their issues? I know from experience that if you have an offensive lineman that is good at the bench press, he is probably not going to spend the necessary time doing rows or pullups because he isn’t good at those. As a result, his weight training is going to compound the issue with his sport that is predominantly horizontal pushing. As he overdevelops his anterior chain, his posterior chain will not be able to keep up, likely altering his posture and creating the potential for a back injury.
Once the potential injury is identified, a proper program would include exercises and movements to alleviate the asymmetries and address weaknesses. Most often the weaknesses are around joints. In order to reduce the potential injury, strength and conditioning professionals must include ways to both strengthen these joints and create stability around them. All parts of the movements must be addressed and executed through full ranges of motion also. This includes eccentric movements as well as the deceleration phase, which often times are overlooked.
I am a firm believer that non-contact injuries have no place in sports. Athletes should follow a strength program that looks to correct inefficient movement patterns before making them stronger. If you imagine athletic performance like a pyramid, the basic movement patterns and functionality can be considered the base/foundation. In order to build a bigger pyramid, you must first build a bigger base.