During acromioclavicular (AC) injuries, the subclavius muscle is overused, trying to limit motion at the AC joint. The subclavius simply means under (sub) the clavicle (collar bone). Luckily, simple self manual techniques can alleviate an overactive subclavius muscle, improving its strength and helping protect the shoulder from excessive stress. Directions: With your thumb, apply a vertical and posterior force directly under the collar bone (clavicle). Move the thumb slowly on this muscle, across the entire clavicle. If tender, move slower, sometimes stopping on extremely tender areas. Perform this exercise for 2 – 3 minutes.