Figure 1. The muscle conditioning procedure.

A, triceps and biceps EMG. B, elbow angle. Subjects were asked to extend their reference arm and contract triceps (extension conditioning), then to relax while the experimenter moved the passive arm to the test position where it was placed on a support. Subjects were asked to match the reference position (dashed trace, B) with their indicator arm (continuous trace). They were to declare when they believed they had achieved an accurate match (arrow). The conditioning procedure was then repeated with the arm flexed and a conditioning contraction carried out in biceps (flexion conditioning). This was followed by another position matching trial.