Starting Position: You and a training partner should have specialized resistance x-pattern resistance tubing with four handles so that two people can use it at the same time; or take 2 pieces of standard resistance tubing with handles and cross them to interlink them and create a 4-handled pattern. You and your training partner should stand facing each other with your feet hip-width apart and the right foot slightly in front of the left to create additional stability; your knees and hips should be slightly bent so that you each can sink into your hips and contract your abdominals (bracing) for additional stability. You and your partner should each position your body with the spine in neutral (normal-to-flat), shoulders depressed (no shrugging) with scapulae retracted (squeezing shoulder blades together). You and your partner should each keep your chest held up and out, with your head in line with your spine or slightly extended (raised). Grab the handles firmly in both hands and hold them so that your palms are facing the ground and pull back slightly to create opposing lines of pull.
You and your partner should each maintain an abdominal contraction with your feet planted on the floor to create stability through the hips and core. At the same time you and your partner should each pull back on the handles, the pulling motion should be initiated from the shoulder blades (which are rectraced), continue holding on to the handles but think about pulling from the elbows to engage the upper back and shoulder muscles.
Once you and your partner have pulled the handles back (into shoulder extension) you each should hold your shoulder blades retracted in an isometric contraction. With both arms held in an isometric contraction you and your partner should each allow your right arm to come forward in shoulder flexion (arm moving forward towards your training partner) while maintaining the left arm in a position of shoulder extension.
Once you and your partner have each allowed your right arm to move forward and pulled it back, you each should keep the right elbow next to the body with the right shoulder held in an isometric contraction (allowing no movement) while you each reach the left arm forward (the shoulder moves into flexion). Continue the abdominal bracing and alternate the arm movements, you and your partner should work together to provide resistance to one another while simultaneously pulling back on the bands to keep the tension.
Exercise Variation: Start with slow, steady consistent movements to become used to providing manual resistane through the tension of the rubber tubing; to increase the intensity you can either stand further away from each other to create additional tension on the rubber or increase the speed of the movement to make it more of a power-based exercise.