health concerns and picking a kayak

[Sdspeed]

I was wondering as an old timer with some aches and pains what part of my body is gonna be trashed the most fishing from a kayak in our local waters?
Haven't bought yet so with these health concerns does it narrow down which kayak might be more comfy and perhaps easier on the bod?

Also since I'm still looking and learning is there any exercises I can start on at home to limit my pain when I make the leap?

tks !