Those who suffer from stiff shoulders often also experience stiffness in their armpits.
Since this area is often difficult to notice, let’s consciously work on loosening it.

Extend both arms towards the ceiling, cross your hands, and bring your palms together.
Simply extending your arms as far as you can above your head will stretch your armpits considerably.
Furthermore, tilting your upper body from side to side will stretch not only your armpits but also your sides.

Next, get on all fours and place your hands slightly in front of you.
Lower your hips as much as possible.
At this time, focus on bringing your shoulders as close to the floor as possible to stretch your armpits.