my opinion after nearly 40 yrs involvement wi racing / running dogs is of course there has to be a balance but the real dogmen know that every dog is different, some love walking others need it to keep them keen, overrunning can aggrevate some injuries, walking them early does toughen up pads, tendons, joints etc, running helps them find their feet and balance when young etc. i think its a question of knowing your dog / dogs and treating them accordingly