Watch P90X2 - X2 Chest + Shoulders + Tris (2013) : Full Movie Online Free Known as your pushing muscles, the chest, shoulders, and triceps will learn to function better than ever before with this workout. We accomplish this with creative uses of instability, and always forcing movement out of an athletic position. By forcing movement out of an athletic position, you'll push chest, shoulders and tris to perform at a higher level.