Providing arm weight support increases range of motion and breaks abnormal movement patterns such as flexion synergy. A simple robot with one actuated DOF could be ideal for proving arm weight support and enhance feedback in home settings. This article briefly presents the kinematics and optimization of such a robot– MARS (Motorized Arm Support). It is common to add redundant degrees of freedom (DOF) to increase the robot’s workspace. Thus, two kinematic chains of MARS are considered, 4-DOF MARS and 5-DOF MARS with one redundant DOF for the optimization problem. The 5-DOF MARS reaches 4.4% more work area of the arm but increases the complexity of the system as it requires additional mechanical elements such as dampers to prevent impact forces at the arm. Thus, to keep the system simple, the small loss in work area is considered acceptable and the 4-DOF kinematic chain of MARS is chosen for further development.