This stretch is for your pecs which are your chest muscles. Usually when I see paddlers do this stretch they twist too much with their body which puts a lot of force through the front of the shoulder and stretches the shoulder capsules instead of the chest muscles. To keep this from happening use a doorway or a corner of the room and step forward with one leg to help keep your back neutral; lean forward until you feel a stretch through your chest and you can see now there is much less stretch happening directly at her shoulder. This is important for paddlers because stretching the shoulder capsule will make your shoulder more unstable. You can also move your arms up higher or down lower to feel the stretch in different parts of your chest.