I know hills and poles are great, but I've got neither. So far I've been taking him for 20 minute walks around my driveway (a big circle driveway) he gets very tired and starts lagging behind after about 10-15. Just walking. I also turn him out, after about an hour outside (even with hay) he stands at the gate and wants to come in. There is snow out there, which I had him walk through a bit today, as it makes him pick his feet up higher, but he kept tripping - so I went back to the driveway. It's not icey, he's not slipping and it's soft, he just seems to stumble.
For reference this is what he looks like: