What the video shows
It shows how the shoulder blade contributes to arm movement and why the direction and timing of that movement matter around the shoulder.
Video
Shoulder-blade control during arm elevation
The video shows that the shoulder blade is not a fixed base. During arm elevation it needs to move in coordination with the shoulder joint to distribute load more comfortably.
How this may feel
With reduced control, some people notice pressure, fatigue or pain around the shoulder and shoulder blade, particularly during repeated overhead activity.
A sensible next step
Exercises are not only about shoulder strength. They often include shoulder-blade control, movement pace and a gradual increase in load.