Hard soled shoes. Like, old-school combat boots. I'm *just* old enough to have been issued the old "black Cadillacs" from the first time I went to OCS and the drill instructors swore by them. We all (well, I at least) thought they were heavy and clunky and uncomfortable and would wear the jungle boots as much as they let us. And then after getting out into "the fleet" you'd wear the sneakerlike "tactical" boots favored by police and SG-1. Hi-Teks. Bates Lites.
Well since getting a dog I walk a lot and after, say, 50 I'd just randomly tweak my back walking and be miserable. For whatever reason it occurred to me to break out the "black Cadillacs" and damned if they don't help your back recover.
On a related note, I wound up heavy into Indiana Jones cosplay and eventually assembled a fairly accurate get-up. The shoes were Ford's own preferred shoes: Alden's (I forget the model) with an orthopedic sole. I couldn't justify the cost of actual Alden's, but I got one of the last pairs of a good repro a guy named Todd Coyle used to sell and was somewhat surprised at the time that there was nothing particularly special about the sole. It was just a stiff, hard sole. But after my experience with the combat boots I understood. A stiff, stable sole on a boot is like a foundation on a house: It provides stability and protects the spine. I still don't wear either every day for various reasons, but when my back starts feeling sore, I'll rotate the combat boots into my footwear for a time until my back fees better.
(On a side note, a lot of Ford's acting choices in "Raiders" are dictated by the costume. The way he rocks heel to toe as he steps across the booby-trapped temple floor in the beginning? That's the way you walk when you walk slowly in that particular shoe. When he's stealing the truck containing the ark and he's hunched over the steering wheel? He isn't being intense or focused. You have to sit that way when you're wearing a fedora in a truck or a car with a headrest. Otherwise the brim bumps against it.)