The way in which the multi-degree-of-freedom musculoskeletal systems are coordinated adaptively during skilled actions as diverse as walking, running, grasping, handwriting and reaching for a target is one of the fundamental issues in understanding human movement. The degrees of freedom of a system are "the least number of independent coordinates required to specify the position of the system elements without violating any geometrical constraints." Generally speaking, the larger the number of degrees of freedom in a dynamic system, the more difficult it is to make the system behave as desired due to the nonlinear interactions between degrees of freedom. It is known that skilled actions are planned in a corresponding-task spatial coordinate system. The planned actions must be transformed into body (joint) space form and muscle space form. However, generally, the number of degrees of freedom in the musculoskeletal system engaged in a task exceeds the number of degrees of freedom needed to specify the task to be carried out. The motor control problem is highly indeterminate with respect to most tasks. Therefore, it is necessary to find constraint conditions for transforming a planned trajectory or force in the task space into that in the joint or muscle spaces. In the present paper, we discuss the roles of motor impedance in reducing the redandunt degrees of freedom on the musculoskeletal system. First, we give the motor impedance transformations among the task, the body and the muscle spaces, and then inverse kinematics solutions using the impedance constraints. Further, it is shown that in crank rotation tasks, the subjects determine limb postures based on the hand and joint impedances.