This double-blind randomized-controlled multi-centre study will investigate a novel three dimensional scapular-humeral mobilization treatment technique and protocol for decreasing HSP, and compare it to the current standard. The protocol includes scapular mobilizations in upward/downward rotation, anterior/posterior tilt about a horizontal axis, and medial/lateral tilt about a vertical axis, all of which are synchronized in alignment with humeral flexion, abduction and external rotation.