Abstract: An arm exercise system (10) comprising an arm trolley (14) having one or more support wheels and which is arranged to support a user's arm for movement over a surface via the wheel(s). The arm trolley (14) also has an actuator(s) associated with one or more of the wheel(s) and which are operable to apply a level of braking to resist movement of the wheel(s). The system (10) further comprises a motion tracking system (16) that is arranged to sense and track movement of the trolley (14) over the surface and generate representative position data relating to the movement of the trolley. A computer system (18) is arranged to receive the representative position data to enable a user (12) to interact with a program running on the computer system via movement of the arm trolley (14) over the surface.