Here are the ASMI recommended limits.
Pitch Count and Other ASMI Recommendations
Pitch Counts
Age Max. /Pitches Per Game/ Max. Games Per Week
8-10 52 2
11-12 68 2
13-14 76 2
15-16 91 2
17-18 106 2
Recovery Times
Age 1 Day Rest 2 Day Rest 3 Day Rest 4 Day Rest
8-10 21 34 43 51
11-12 27 35 55 58
13-14 30 36 56 70
15-16 25 38 62 77
17-18 27 45 62 89
Age Recommendation For Learning Various Pitches
The survey also presented recommendations for the age at which a player could learn different types of pitches. These are listed below.
Survey - Age Recommendation for Learning Various Pitches
Pitch Age
Fastball 8 - 10
Change-Up 10 - 13
Curve ball 14 - 16
Knuckle ball 15 - 18
Slider 16 - 18
Fork ball 16 - 18
Screw ball 17 - 19
Pitch Count Plus Other Factors
Other factors to take into account as you determine, "How many pitches should I allow my player to pitch?".
Some Additional ASMI Survey Conclusions:
A pitcher should be limited to two appearances per week.
Participation in multiple leagues, playing other positions, and practice should be considered when defining and regulating rest.
Improper technique is a major factor in injury potential.
Conditioning of the throwing arm and entire body can reduce a young pitcher's risk of injury.
While the number of pitches should be limited, the young athlete should be encouraged to throw. This includes playing catch, playing other positions besides pitcher, and practicing pitching. When symptoms of arm discomfort or fatigue arise, longer periods of rest are recommended.
You can find the complete ASMI research at:
http://www.asmi.org/SportsMed/youth/PITCHCNT.PDF