Theres a simple exercise that will expose an upper back weakness almost immediately. Its called scapular retraction, and all you need is pullup bar to perform the self-test. If you cant hold this exercise for 10 seconds, then you have glaring weakness in the muscles around your shoulder blades. Thats important because a weakness in these muscles leads to unstable shoulders—and that limits your strength and muscle gains in nearly every upper body exercise, including the bench press and a...

Original article and pictures take http://www.menshealth.com/fitness/exercise-of-the-week-1 site