Rowing is excellent as it gives you good core strength which is useful for hiking, and a bit of cardio.  Obviously as others have said, you want to target the legs, shoulders and core mostly but you have to be very careful you don’t only work those muscle groups or you will end up getting recurring issues in other areas as your body pulls itself out of shape.  I found working on my lower back useful (dead lifts aren’t fun but by god they work) for rocking in and out a lot from a full hike to sitting on the side deck as it takes some of the pressure off your abs.

My gym also has a bar with some dangly strap things hanging down with handles on them, so I do something I’ve nicknamed ‘wire hang pullups’.  I kick off something at a trapezeing angle, then dangle on the ‘handle’, then pull myself up with one arm until the handle is touching my chest.  Build to four sets of 8 reps then watch as you never have any issues with mucking about on wires again.  Quite why I bother when I only charge about in a laser most of the time I have no idea, but there you are.