Turning a steering wheel is a typical example of human movements that are constrained by the physical environment.The constraints decrease the mobility of the human arm and lead to redundancy in the distribution of actuator forces (either joint torques or muscle forces).Due to this actuator redundancy, there is an infinite number of ways to form a specific arm trajectory.However.humans form trajectories in a unique way.To understand how humans resolve the redundancy of the constrained motions and specify the hand trajectory, we examine human arm movements in manipulating a steer wheel.In this wore a musculo-skeletal model of the upper limb is presented.