There is a valid concern of sports attrition related to early, specialized intense training among youth athletes. In a study on burnout, earlier specialization in swimming resulted in less time on the national team and earlier retirement compared with later specialization. In ice hockey, players more prone to dropout began off-ice training at a younger age, while they also invested a larger number of hours in off-ice training at a younger age compared with those who continued participation. Other studies in sports, such as swimming and tennis, suggest that retirement from sports may be the consequence of burnout, which young athletes may experience with continued intense and specialized participation.
Source: Sports Health, Published online August 6, 2015