HOW: While keeping your elbows at your side, focus on spreading the arms as far as you can while holding onto a band. This time perform this QUICKER. Initiate this motion with the shoulder blades and allow your arms to follow. The firmer the band or the more you tighten up the band, the more challenging this exercise will become.
FEEL: Primarily the muscles on the inside of the shoulder blade with some assistance with the muscles on the back of the shoulder.