9 Active Tension Drills for Shoulder Mobility VAHVA Fitness. Active tension drills to build shortened end-range mobility in the shoulders, targeting especially the trapezius muscles! These shoulder mobility drills add both strength and flexibility to your shoulder girdle (scapula). You will be surprised how tough the prone exercises below can be. Although these drills can be labeled as "mobility drills", you can expect to build some serious strength and size to many of your scapula muscles. This