The systematic analysis of rotational bands for medium and heavy nuclei (covering the mass region from 100 to 244) has been studied through the theoretical model, the variable moment of inertia with softness (VMIS),and the experimental data. This model used to investigate the behavior of backbending and upbending in nuclear moment of inertia. A systematic study of the level structure up to spin 20⁺ of the selected nuclei including soft as well as good rotors and exhibit back bending or up bending are performed. Good agreement between the theoretical model and the experimental data are observed.