Age	15 years	165
	16 years	640
	17 years	481
Mean age (years)	16.2 ± 0.7
Gender	Mail	1288
Gender	Female	0
Mean age of initiation into baseball (years)	9.6 ± 2.2
Main position	Pitcher	292
	Catcher	135
	Infielder	480
	Outfielder	356
	Others	25
Total amount of practice per week	Days	6.5 ± 0.6
Total amount of practice per week	Hours	27.2 ± 7.5