Haptic training was based on a robot-assisted exercise protocol specifically designed to treat cerebellar and motor symptoms in persons with MS by counteracting, respectively, incoordination and muscle weakness. The exercise is based on a motor task - interaction with a virtual mass-spring system under the effect of a resistive load - that requires sophisticated coordination skills. Task difficulty (the time constant of the mass-spring system) and the magnitude of the resistive load (stiffness magnitude of the resistive spring) were automatically adjusted to the individual subjects' upper limb impairment.