Reverse Fly with Scapular Squeeze
Start in a standing position with good posture and your arms straight out in front with your hands just below shoulder level. Keep your shoulders as relaxed as possible and slowly move your arms horizontally out to the side until it feels like they can’t move any further.
At that point, you should feel some muscle tension in your mid/upper back muscles. Then, actively contract or squeeze those muscles and try to use those muscles to move your arms a little further. This should significantly increase what you feel in those muscles. Keep squeezing your back muscles for 3 to 5 seconds.
Perform up to 15 reps of this exercise and stop if you aren’t able to keep your shoulders down and relaxed or you feel a significant decrease in the amount of tension generated by your back muscles. If it’s too difficult to maintain good posture while standing, you can perform the exercise seated.