Over time, the tendons of your shoulders start to wear down. It’s usually a combination of things: spending hours every day hunched over the computer, bench pressing weights that are too heavy, just getting older, which results in your tendons become less flexible.
You can make these problems worse if you do the wrong kinds of exercises. If you’re beyond forty and feel discomfort in your shoulders, don’t lift overhead. The worst exercises are the ones where you press the weight from behind your neck.
For your shoulders, don't lift overhead. It's even worse when you press the barbell from behind your neck, like this guy.
When you press the barbell behind your neck, your shoulders externally rotate, causing the tendons to rub against the bones in the shoulder. Even lifting the weights in front of your head, though not as bad as behind the neck, can make your shoulders ache.
What to do? The trick is to work out the shoulder muscles without externally rotating the shoulders. A terrific exercise is the Scaption.
Preparation
Hold the dumbbells at your side, with palms facing the side of your body.
Contract your glutes, draw in your navel, and retract and lower your shoulder blades.
Movement
Raise both arms, thumbs up, at a 45-degree angle in front of the body, until your arms are parallel to the floor.
Slowly return your arms back to the side of your body and repeat.
Give scaptions a try. Your shoulders will thank you.