As I mentioned in False Carpal Tunnel from Tight Pectoralis Minor — if that muscle is tight it can cause the shoulders to round forward and create pain between the shoulder blades.
If very tight, it can cause numbness or tingling in your fingers, hands, and even up you arm. If very tight it can also pinch an artery leading to the hands, causing poor circulation in them.
One way to tell if the Pectoralis Minor is causing the numbness in your fingers is to raise your arm. If after a few minutes the numbness your numbness is worse and if lowering the arms makes it better, the problem is most likely a tight pectoralis minor muscle.
If you get numb hands riding a bicycle, motorcycle, driving, or doing anything else where your arms are somewhat up — BUT lowering them relieves them — look to the pec minor. Forearm muscles are also frequent culprits as well, but with them it doesn’t make any difference in the feeling whether your arms are up or down.
However unless you loosen the pec minor, your hands could become numb most of the time.
Because most of us work with our arms in front of us. This muscle is usually tight on almost everyone. But seldom do we feel any pain there. Because they pull the shoulders forward, the muscles between the shoulder blades (the rhomboids) are continually fighting to keep your shoulders back.
The solution is to loosen the pectoralis minor (First go to: False Carpal Tunnel from Tight Pectoralis Minor) then watch the video below.
The other thing to do is strengthen the muscles of your upper back. (I’ll get to that another time).
This video shows stretches for the Pectoralis Minor.