The specification describes endoscopes that enable varying stiffness of an insertion portion in an endoscope assembly. In one example, an actuator operates either a spring or a flexible tube to vary stiffness of the insertion portion. In alternative examples, an elliptical wheel arrangement or screw mechanism provides a means to increase stiffness of the insertion portion of an endoscope assembly. In further examples, fluid and gas may be used inside the insertion potion to vary stiffness by varying pressure of the fluid/gas.