The supine horizontal shoulder abduction exercise strengthens the muscles in your shoulders while promoting good posture. It is done in the supine position to help stabilize the back which helps isolate the shoulder muscles.
Begin lying on your back on a mat with the end of a resistance band in each hand. Bend your knees so your feet are flat on the mat. Hold your arms out straight in front of you shoulder-width apart. Palms should be facing up and the band should be in front of your chest. Make sure that there is a little tension in the band before you begin.
Using the muscles between your shoulder blades and behind your shoulders, slowly pull your hands away from each other while holding the band in both hands. Keep your elbows straight and your hands at chest level throughout the movement. Continue until your arms are straight out to your sides, forming the letter “T.”
If you find there is too much tension to open your arms all the way, begin with more slack in your band.