Amazing how paddling technique has changed , I remember when Dave Kalama was saying to reach reach , when you do that with your shoulder it puts the joint in a bad position ive found , and your shouders get sore very quickly especially if you've had previous issues. Its like when you do weights or lifts like deadlifts and chin-ups you need to keep your shoulders tight in the joint and transfer the load to the muscles. A good way ive found that helps is keep a slight bend in the upperarm , and keep your wrist parallel with the paddle shaft , and when your paddle is set think about a boxers jab instead of forcing the paddle down into the water with your shoulder. Changing up your hand positions helps to I rekon , and your feet for that matter. To help stop using the lower back so much by over ending a simple solution is lift your head and look further out in front of the board , you see a lot of people looking down at the nose of their board or at their feet this causes bad balance and a tendency then to overbend. Your body follows where the head goes