Figure 3

Forces experienced by the person manipulating an impaired limb vary depending on the manipulation strategy. Different abnormal conditions can be undistinguishable if forces produced by the movement are not sufficiently different. (a) Circular probing motion (note that there is not much difference between the forces produced by abnormal shoulder and bi-articular muscles; (b) pulling and (c) semi-elliptical probing motions (note that the forces produced by the different abnormal conditions can be discriminated by these two motions).