This is an exercise I’ll use a good portion of the time as part of an upper body warm up. I’ll use use it working some one back from a shoulder injury also. The reason I like this exercise is because when done right, it really gets the lower trapezius muscles firing. At the same time it’s trying to open the pec and anterior shoulder area. Focus on keeping your entire arm back against the wall and only go up as high to the point where your arms start to come off the wall. If you can straighten your arms out to this point, great.