Being able to keep your shoulder blades stabilized is very important for shoulder strength, health and function. On our bikes, being able to resist the “hunched shoulder” posture is important for keeping the tension out of your neck. In addition, being able to have your upper back in a flat, strong position gives you better control of the bike and balance on the trail.
The wall slide is a staple exercise in my facility to counteract the effects of riding posture, which also happens to be desk posture and sitting in your car posture. Do 2 sets of 10 reps a few times a week and watch what happens to your posture and shoulder health.