A clinical motion analysis protocol was developed to measure the coordinated movements of shoulder-girdle and humerus (girdle-humeral rhythm--GD-H-R) during humerus flexion-extension (HFE) and ab-adduction (HAA), through an optoelectronic system. In particular, the protocol describes the GD-H-R with 2 angle-angle plots for each movement: girdle elevation-depression and protraction-retraction vs HFE, and vs HAA. Each of these plots is further divided in two subplots, one for the upward and one for the downward phases of the movement. By involving 11 participants and 2 operators, we measured the protocol's inter-operator reliability which ranged from very-good to excellent depending on the angle-angle plot (median values of the inter-operator coefficient of multiple correlation for the angle-angle plots higher than 0.94). We then computed the subjects' average control patterns, together with statistically meaningful prediction bands. +/-1SD confidence bands were also computed and their width ranged from +/-0.5 degrees to +/-4.6 degrees. Based on these results we could conclude that the method is robust and able to identify even limited differences in the GD-H-R.