[FISH11]

It often has to do with how you adjust the straps for the seat back. don't want to be leaning back too far or too forward. It needs to be high enough on the back for support (about 1/2 way up your back, definitely above your waist), also if your PFD is in the way of the seat back, then you need a better PFD (NRS Chinook). If you're not seating in the right angle. then your back is going to be sore from the paddling and not from just sitting.