Proprioceptive illusions induced by muscle vibration: contribution by muscle spindles to perception?

When vibration of 100 hertz was applied to the tendon of the biceps or the triceps muscle, the subject made a systematic misjudgment of the angle at the elbow. During contraction the error could be as much as 40 degrees. The subject thought that the elbow was in the position that it would have assumed if the vibrated muscle had been stretched.