The effect of early specialization on long-term athlete development is evidenced on physical and psychological levels. Harre et al. (1982) compared the major differences in athletes who specialized early v those who had a multilateral development:
Early Specialisation v Multilateral Development
1. Quick performance improvements v Slower performance improvements
2. Best performances aged 15-16 years v Best performances aged >18 years due to physiological/psychological maturation
3. Inconsistency in competition performance v Consistent and progressive competition performances
4. High % of burnout and quitting by 18 years v Long athletic career
5. Increased risk of injury due to forced adaptation v Fewer injuries due to progressive loading and better physiological development
The evidence in favour of multilateral development where young athletes participate in as many sports as possible until the ages of 14-15 years, versus early specialization is clear.