Just to clarify my post.
I'm not advocating running hares at 4 months (I know people who have :o ) or lamping your dog silly at a young age.
As I said though my present pup has been out since she was jagged. at this age they can’t run anything, my bitch would just watch, and hopefully learn. As they get older then yes you hold them back but not too much, let them scramble over obstacles, investigate kills made by the other dogs etc.
As Meerihunter said they need to ‘trip and fall and bump themselves’ to learn to negotiate the ground they are expected to run on.
IMHO to give a pup