Balance uses visual, vestibular, and somatosensory (proprioception mainly) systems to maintain a line of gravity from a base of support, minimizing lateral sway from that equilibrium. Balance, an often over-looked component of fitness, is a skill that can be tested and improved in a range of ways. One such way that we advocate for is using an unstable surface or specially-designed tool, like the Strongboard Balance Board
Your shoulder joint does not act in isolation to create movement in your arm. The muscles of your shoulder and scapula ( shoulder blade ) act together to create all movements of the arm.
Often the importance of strengthening the muscles controlling the shoulder blade is forgotten. Having a strong, stable, and well moving scapula is important for all baseball, basketball, swimming, overhead lifting or any sport involving the arm.