It's hard to judge 'how hard the tour might be on your back' without knowing your back and its limitations.
But I don't recall much climbing if that helps.
You are in a safety harness which has a brake so basically all you do once on-zip is to tag along for the ride: the harness
supports your weight as you basically 'sit' in the harness.
(Big diff from Costa Rica where we had to brake ourselves with much longer, higher zips that went much faster.)
I guess if you took a couple of aspirin or anti inflam before zipping, you'd be fine. I went with my daughter and don't recall having any pains or aches afterward (course, that might have been the tequila!)