Lately I have been using light club swing training to improve my thoracic spine and shoulder joint mobility. I use 2.5 pound or 5 pound plates or a 5 pound compact club.
This sort of training which involves swinging the club/mace about your shoulder joint greatly improves your mobility and strength in extended range of motion. Look at this illustration to visualize the 3 member, two ball-in-socket joint dynamic system you create when you swing a bat or club. It also helps is the knob of the club is taped up to provide a spherical grip on the end of the club which creates the dual ball-in-socket joint swinging system.