A stability ball inflation and deflation system includes a stability ball with a bore, and a plug within the bore walls. An air-control module engaged within the axial channel of the plug selectively allows air to pass in one or both directions. The air-control module includes a one-way air valve, and a cap releasably sealable to the plug. An airway extending from the one-way valve provides fluid communication with the interior of the stability ball. An inflator adapted to engage the one-way air valve may be removably coupled to the air valve, and provide air passages to direct air from a pressurized air cartridge into the stability ball.