How old is your pup? You never want them to be excessively large for their frame (health problems) but you can begin to do some light conditioning once they are at least close to done/slowing growing starting around a year and a half to two years or so. Trying to accelerate growth, adding too much muscle as well as too fast particularly if their frame is still in major growth stages just cripples them in the long run. In most cases people don't see much of a need once their pup is done growing which can be into the third year. There first year they grow mostly 'up' and the second they grow mostly 'out' putting on their adult weight and muscle. You don't want to put too much stress on your pups bones and joints and cause injury and long term forever damage, you both pay the price for that. They also probably aren't supposed to be as big as you may be thinking and your pups lineage is a factor as well. The first link is advice to properly begin to condition them if/when your pup is old enough. Second is your breed parent club.
www.pitbulllovers.com
www.amstaff.org
www.wildheirlabradorrescue.org members.tripod.com
www.pitbulllovers.com
www.amstaff.org
www.wildheirlabradorrescue.org members.tripod.com