I didn't know what your major study was, you are probably the most fit of the group.
I don't know if you were ever a bicyclist , if not I'm not suggesting you start now....... but if you have enjoyed riding in the past now may be the time to get back on one. It is my favorite way got get some movement, 0 impact to the joints or close to 0 and with time it'll put a fellow in shape.
Today I am getting my exercise by looking for my wallet! I believe I've put on half a mile right here in the house plus lots of trips up and down the stairs and runs to the truck. You know the drill, maybe it's really there and I just missed it