Prolonged immobilization results in several physiological problems. It has been demonstrated that standing exercise can ameliorate many of these problems. Standing exercise can be efficiently performed by the help of functional electrical stimulation (FES). A novel robot mechanism for unsupported standing of paraplegic persons providing balancing exercise was developed. The balancing strategy is based on voluntary activity of the paraplegic person's upper body and artificially controlled stiffness in the ankles.  The importance of the use of cognitive feedback during balancing exercise was also studied.