Well, just buggy or grass ski for a bit after not doing it for a while and you'll definitely feel it in your chest, like you've been doing pull-ups.
(provided you're not using a harness!) So that's exercising your back and arms.
It's a lot of hand-eye coordination in order to control the kite. And balance, as you try not to end on your rump!
And then of course there is always the 50 yard sprint when you loose control of the kite and have to go chasing after the now tangled mess!
(Fortunately I haven't played that game in quite some time!But I remember when I was first starting to buggy, in a field surrounded by tall trees and
swirly winds, I had the kite ripped out of my hands and the buggy clean tipped over about 3 times in 20 minutes!)
Good Luck
-chip