Figure 2.

Illustration of multiple redundancies with the example of hammering on an anvil. Intrinsic redundancy: An infinite number of combinations of the three joint angles of the arm can place the tip of the hammer in one location in the plane. Extrinsic redundancy: An infinite number of trajectories can hit the anvil at one point. Task redundancy: The anvil can be hit at an infinite number of contact points, as the target is not a single point but an area. The shown trajectories are the original recordings of Bernstein³⁸. Not shown is that similar intrinsic redundancies exist due to multiple muscles and muscle fibers achieving the same joint configuration.