Abstract: A horizontal support arm is mounted for upward and downward movement on a vertical support column. An interface unit having an actual mass value is disposed on a free end of the horizontal support arm and is adapted to be grasped and lifted by a human subject. A simulated mass value independent of said actual mass value may be set for the interface unit, and the amount of vertical force exerted by the human subject upon the interface unit is measured. An exercise control unit provides for controlled vertical movement of the interface unit as a function of the simulated mass value such that the interface unit responds to a lifting force by the human subject in a manner that simulates the inertia of an object having a mass value equal to the simulated mass value in a gravitational field.