International Institute of Cricket Umpiring & Scoring
ECB bowling restrictions
"We have a young fast bowler, who really is very quick. He may be a bit erratic sometimes, but there's no doubting his shock value, and he's obviously going to go on to pick up lots of wickets. He likes to bowl long uninterrupted spells, but is always instructed by the umpires to come off after a certain number of overs, even though his dad, who also plays for us, agrees to him bowling for longer. Comments, please"His dad ought to think long and hard! The England and Wales Cricket Board (ECB) introduced these limitations on the number of overs young fast bowlers may bowl to help prevent them breaking down as bowlers when they are older, because they were allowed to bowl too many overs before they had finished their physical development.
Read more about the ECB bowling directives