Big 5 - Overhead
In the gym we look at the spine first. Whether it's during movement, when mobilising a joint, when there's pain or dysfunction. Just think of it like a house - You can have the flashiest equipment, a big bed, fancy wallpaper, but if the foundation is weak you're screwed. The body is no different. Biceps and pecs look great but they won't hold the house up.
Whether you're an athlete, a desk warrior, a mother, a tradesman, whatever. When you strip it back you're a human being. You're not a special snowflake, this does apply to you and you can't ignore it.
With that out of the way we've established that the spine is a pretty big deal. Not only is it the structural foundation for which your extremities originate and organise themselves from, it houses your nervous system. If the brain senses a threat to the spine, good luck functioning optimally with your limbs.
The organisation and stability of the spine is the central theme for all of the Big 5 positions. The reason having full capacity in each of these positions matters comes down to spinal health on a global level, and the health of your joints on a local level.
Overhead range of motion (or lack of) implications and mechanisms
Putting your arms above your head sounds pretty rudimentary right? However the inability to do so is like an epidemic in the gym (I say the gym because it's a formal setting where seeing movement is easy, but really I mean life in general). The mechanisms taking place when range of motion is lacking look like...
Usually during the task of putting something above your head, the target point or end range of motion is fixed. Whether it's hanging out the washing or snatching a barbell, the finish position is governed by something out of your control.
This is important because your body wants to get to this position whether or not your mechanics are sound. If you don't have full (normal) overhead range of motion your spine will compensate, feeding in some slack to allow the movement to be completed.
The video below shows how the spine changes shape during movement to achieve end range. Movement of the spine during motion under load is not a good thing. Like I said in the previous post, you might be able to buffer it for thousands of reps but eventually it will get you.
Going overhead with the arms can cause some issues to the shoulder joint (glenohumeral) itself if things are tight and restricted and not where they're supposed to be. Getting your arms above your head requires flexion of the shoulder (movement occuring between the humerus and the scapula), but also some upward rotation of the scapula itself.
For every 2 degrees that the arm moves overhead, the scapula rotates upward 1 degree. If the shoulder blade didn't rotate upward as the arm did, your arm would run into the acromion process, pinching the tissues that sit in-between the bony process and the humerus.
Using the picture above, imagine the shoulder blade is fixed and doesn't move. You can see how if the arm was to move towards the overhead position, it would hit the acromion before it got there. When the scapula moves in sync with the arm, the inferior angle (labelled scapula in the photo) rotates outward and upward letting the whole system move together, bringing the arm closer to the overhead position without the impingement.
The photo below demonstrates this
The Fix - Hanging
Hanging from an object is pretty cool for a lot of reasons. It'll strengthen everything in the system from your shoulders to your grip. This is important to understand because being a system of systems you are only as strong as your weakest link, this being your grip. Your arms and shoulders can only pull what your hands can hold onto. Strength aside, hanging is good from a mobility sense because it means you can spend some time passively in an overhead position while using gravity to aid in a stretch. Not only hitting whatever areas are restricted, but promoting some upward rotation of the scapulae as well.
Just make sure you prioritise your spine by keeping a little bit of tension on with your glutes, and maintaining the relationship and organisation of your ribcage to your pelvis. Once you've set your pelvis by squeezing your butt, lock down your abs, as if someone was going to whack you in the guts.
Good Not so good
You can mix it up by trying different combinations. Try one arm, traversing the bar, swinging side to side. If you have a pull-up bar that has parallel handles (meaning that when you hang your palms face inward towards each other) then using these will externally rotate your shoulders slightly.
Full range of motion overhead requires not only shoulder flexion (arms to the sky) but external rotation of the shoulder. Meaning that when you put your hands overhead your palms face inward, this will wind the system up making it stable. You could exaggerate this position by hanging in a supinated grip (palms towards your face).
Like any process, it needs to be progressively overloaded to continually adapt to the stimulus it creates. Hanging from an object unassisted could be extremely difficult for some people to manage, and do more harm than good. If so, just start with your feet on the ground or a box so you can adjust the amount of your body weight that your shoulders, arms, and wrists are taking. Start with 20-30 seconds at a time, and build up to being able to hang for several minutes.
Loads and forces and heavy stuff
The way gravity affects you while you hang from an object is called a tension force. Think of it as gravity trying to elongate your body, and you're pulling in the opposite direction. You could also spend time overhead under a compression force. This would look like a handstand, where gravity is trying to compress your body together and you're pushing away to maintain a position.
The hang and the handstand are a nice couplet of movements to pair together to strengthen and improve the position of the shoulders. However the compressive force of gravity during the handstand is going to create a massive challenge for your midline to maintain a good position, so start with your hands a decent distance away from the wall and slowly work back towards it.