A children's baseball bat with a pressurizable, external hitting zone to selectively control the trampoline effect when a ball is struck by the bat. The hitting zone is provided by expandable tubing wrapped spirally around the barrel of the bat and connected to a manual air pump built into the handle of the bat to increase air pressure in the tubing. A pressure relief valve connected to the tubing allows the user to decrease air pressure in the hitting zone to control the trampoline effect or to decrease the circumference of the barrel.