Identification of intrinsic and reflexive muscle parameters of the human arm in 3D joint space

The mechanical properties of the human arm are determined by intrinsic visco-elasticity and reflexive feedback from muscle spindles and Golgi organs. These properties are important to control stable interaction with the environment. With the aid of a new 2DOF haptic robot, the intrinsic and reflexive properties were estimated simultaneously for the shoulder, elbow and wrist joint during a posture task in the horizontal plane. Amongst other features, it was found that the shoulder had reduced intrinsic visco-elasticity that was compensated for by reflexive control. With this new experimental approach, global mechanical properties can be explained from the underlying neural control of muscles.