An exercise device includes first and second housings telescopically coupled together. A pneumatic cylinder is positioned inside and fixed to the first housing and includes proximal and distal ends. A piston having a piston head and shaft is situated inside the second housing, the piston head separating an interior space of the cylinder into first and second areas. Telescopic movement of the housings causes the piston head to move within the interior space. A first check valve is in fluid communication with the cylinder for adjusting an amount of resistance encountered by the piston head as it travels toward the cylinder distal end. A second check valve is in communication with the cylinder for adjusting an amount of resistance encountered as the piston head travels toward the cylinder proximal end. Pneumatic and check valve communication channels are inside the housing. The device is adaptable to exercise multiple muscle groups.