Plank Scapular Push Ups
To do the Plank Scapular Push Ups, set up in a plank from your forearms with your elbows under your shoulders and your body in a nice straight line from your head to your heels.
Then keeping your core still, pinch your shoulder blades together. Relax back out and repeat.
Do not wiggle your hips or let them sag as you pinch your shoulder blades together. You are not humping the ground. You want to keep your abs braced and simply perform the small movement of retracting and relaxing your shoulder blades to feel your upper back activating.