The sample population of studies such as this one is skewed by the mix. In no instance are ages and abilities matched by capabilities. Those youngsters that specialize in studies like this, do so with a mix of intention - theirs and those intentions impressed by others - fathers, uncles, mothers, etc. To suggest that those that specialize are with abilities par across the board is the basis for the study(s) itself.
What even skews the analysis even more is… " study suggest that specialization at a very young age does not increase the likelihood of an athlete achieving elite status within his/her sport" This quote guarantees the outcome FOR the study, not basing a foundation of the study itself.
Regardless of the age, the term specialization has flaws all it’s own. Specialization suggests that coaching, training and follow through, playing environments and such are consistent and with some sort of validity. As we have read, witnessed and experienced - nothing could be from the truth.
Studies concerning youth athletics has its own built in agenda that suits the author(s), a high percentage of the time. These :findings" mirror the claims of “… increase your velocity by 50% and so on,.” for every reader, regardless.
Nothing of a generic or homogenous nature fills the cup of “finds” concerning youth athletics. Nothing. A better study would be to define by age, physical build, social, economic, and puberty range, the entry and progress of sport specific specialized program - what program, by playing position.
This tries to cover some of what I’m suggesting, by leaves more questions than answers.
The age of single sport specialization significantly differed between groups and occurred at an average age of 12.7 ± 2.4 for high school, 14.8 ± 2.5 for collegiate and 14.1 ± 2.8 for professional athletes.