Yes, the shoulder is very complex but I will try my best to keep it simple and understandable to all, including even the guy that shoulder press in a seated position 105kg in front of the mirror. Most of us believe all the injuries occur in the shoulder either because of shoulder mobility or because of shoulder strength and stability. No disrespect man (or woman), but there is a lot you do not know! Structural, postural, respiratory and nerve dysfunctions are some other causes for shoulder injuries. And yes, weightlifting is the answer!
The shoulder region includes a lot of structures including the humerus, scapula, clavicle, four joints, muscles (depressors, elevators, protractors, retractors, internal rotators, external rotators, flexors, abductors, adductors and extensors), bunch of noncontractile structures such as the nerves, ligaments, labrum and bursae. The fact is that if one of these structures is deficient the risk to develop a shoulder pathology is increased (you can stop rotating your shoulder against resistance of thera band, that is not going to help you fix your rotator cuff tear at all).
The key is to avoid damaging these structures from the first place. And that is where the beautiful sport of weightlifting comes into action (oh just got goosebumps from excitement).
Here are some disadvantages of not participating in the sport of weightlifting that will ultimately lead to unconditioned shoulders and eventually kyphosis of the thoracic spine, shoulder joints pathologies, respiration, fatigue, and sleep problems.
On the other hand, building strong shoulders in weightlifting optimizes correct posture that promotes good respiration, maintains the shoulders structures in good health and therefore occurrence of shoulder pathologies is reduced significantly, enhance blood flow to brain and limbs which decreases fatigue, and promotes healthy sleep.
Two essential movements that I will summarize in weightlifting are the lift off and the overhead press. Both movements are critical for good shoulder health.
First is the lift off, usually people lift from the floor by moving their shoulders and arms forward, while weightlifters move their arms to the sides. This is because weightlifters bring the centers of gravity closer to their body. The result is avoiding placing unnecessary forces on the shoulder joints, strengthening the shoulder stabilizers and facilitation of optimal back posture.
Second is the overhead press. This happens with full elevation of the shoulder. In fancy terms it occurs with scapular stabilization, inferior glide of humerus, external rotation of humerus, rotation of clavicle, scapular abduction and lateral rotation of the AC joint and straightening of thoracic kyphosis (so proud of myself for knowing this). Performing and mastering overhead press (while standing!) is one of the reasons why weightlifters are considered to be the fittest people out there. Not only it requires great mobility but also neuromuscular control, posture, strong shoulder structures and fit body to support the shoulders from head to toe.
To sum up, do your shoulders a favor and start weightlifting, smart, with a coach. Oh, almost forgot to mention, the guy that pressed 105kg in seated position is in the hospital right now. Not only because he ended up tearing his rotator cuff but also because he herniated one of his low back disks 🙁