Lower back pain when paddling

+1 for Yoga, but if that doesnt work definately Orto Spec. I have a herniated disk at L5 (where you bend) and a lateral tear across the same disk, but oddly the back bend releases the pressure off the disk. Try putting your hands behind your back and bending backwards until the pressure relieves and then bend forward as far as you can with your hands still together. Good luck.