Try sitting
on the floor while watching TV for a few hours, even with a pillow under your butt you’ll become uncomfortable in that position.
I tried a comfort seat in my Boreal and that’s what I got, comfort. However, I did not get a seat that allowed the full range of motion I needed to improve my torso rotation, posture, and skills.
You don’t need the Cadillac of seats to be comfortable and this could be a time when less is more. In my Explorer I have an unpadded seat pan and a wedge of minicell foam and couldn’t be happier. I now find I am leaning back less and less on that wedge as my posture and comfort improves. It seemed the more I tried to make it cushy comfortable, the less comfort for my butt and wallet.
Combine some or all of the suggestions above but remember kayaks aren’t Lazy Boy recliners, they are for do’ers, not watchers.
probably your form
I’ve paddled a Feathercraft Kahuna and K-1 for years and found their seats to be very comfortable and adjustable. If yours is a newer model I thought most came with an inflatable lumbar adjustment – have you experimented with that? Also make sure your foot pegs are right so you are pressing against them to transfer power to your stroke. I’ve found that back and hip pain in kayaking tend to come from poor form and from nervousness. the K-1 is a terrific boat but if you have not used it a lot it may seem a bit tippy (the primary stability does feel that way in a K-1) and you may be tensing up due to that. Try practicing leans and sculling in a sheltered area of calm water with it until your body “learns” how good the secondary stability is in that boat and you lose the fear that it will roll on you if you twist your body. Also, try to paddle as much as you can without the rudder in the water. The rudder does slow you down a bit (requiring harder paddling) and learning to track straight and turn without it will give your body more varied exercise as well as increase your skills. Nothing against rudders – when you need one (following seas, beam winds) they can be invaluable, but they aren’t necessary for most casual paddling.
Make sure your paddle is long enough too. I’m 5’ 5" and find the best length for the relatively wide and high-riding K-1 is a 230 or 240 if I’m paddling withoug much gear on board.
Like others have recommended, get some instruction and learn to paddle with your torso, not just your shoulders and arms. The rotational movement not only keeps the muscles from tightening up but helps to build lower back flexibility and ab strength. Adding to that, work on your abs and on your lower back. I like Nautilus and Cybex type dynamic weight machines a couple of times a week for conditioning. Martial arts training is great, too.
FrankNC is totally right
i had sprained my knee a few years ago and from not doing the same activities and using it the same way i had my legs in general get fairly tight, so i ahd to start stretching more and more as i started doing more things, and i noticed a big difference in comfort as i stretched more and more, and noticed a big decline in comfort if i fell off of it and didn’t stretch for a while