Formerly I had a great treadmill from Treaddesk.com but it was too big and heavy for the rv. It didn't fold up or hide away. So I had to sell that and I went on a search for a sturdy yet compact option.
In my Pace Arrow there was a recliner rocker chair that was just to the right as you entered through the side door and just behind the passenger seat. I removed that chair to storage. I wanted a seating position there so I found some replacement feet for my red office chair that I love to replace the wheels (don't want it rolling around while driving). I measure the chair space and the found a folding treadmill that was very sturdy and with a big enough tread for my stride. It fits the space and folds upright with a single pull of a pin. It's perfect.
It has an armature that also folds but I need to have a speaker moved before I'll be able to do that regularly. For now the arms are not a big deal.
In rigged up a shelf on the arms to hold my laptop so I can work will walking.
Presenting my treadmill in my RV!!
Folded up with chair in front: