HOW: Get set-up laying on a long foam roller with it parallel to your spine and in the middle of your back. Make sure your knees are bent with your feet flat on the ground and have your butt and head supported on the foam roller. Prior to initiating alternating arm movement, flatten your lower back into the foam roller and perform a chin tuck (see video for details). If you do not have a foam roller, that is ok you can perform this on the ground. While maintaining this position, alternate raising one arm overhead while the other arm is down by your side, then alternate. Both arms should be moving at the same time with your thumbs pointing up, try to get your arms parallel with your body.
FEEL: You should feel motion happening between and at the top of your shoulder blades towards the base of your neck. You may also feel a stretch in your lats and under your shoulder with the arm that is overhead.
COMPENSATION: Do not arch your low back, do not lose the chin chuck, do not flare your ribs, do not lose your balance off the foam roller. Be safe, if you cannot keep your balance perform on the ground.