This is part three of a comprehensive handstand video series that will help you achieve a strong and stable free-standing handstand. While this video will bring benefit to your training regardless of your current fitness or goals, it is intended as part of larger handstand series. I encourage you to check out Get Ready for Handstands: Wrist Prep, where I discuss preparing your wrists, and Get Ready for Handstands: Shoulder Prep, where I discuss how to get your shoulders ready.
Thoracic mobility, particularly thoracic extension, is a forgotten aspect for many prospective handstanders. Your thoracic spine is your middle and upper back; essentially all the vertebrae that have a rib attached. Thoracic extension eludes many people, as their spine stiffens in the unfortunate position in which they spend hours driving, typing, and sitting.
An open and strong overhead position is essential for a handstand, but even perfect shoulder mobility will never get you there if your thoracic spine cannot extend all the way. If you feel your ribcage lift as you reach into an overhead position, your lower back (lumbar spine) is making up for the lack of movement in your t-spine. This leads to the common complaint of lower back pain from handstand training.
Check out the video below for tools to increase your thoracic mobility, and ways to strengthen this position that will directly improve your handstand.