In my experience, a wood like poplar doesn't make for durable wear surfaces. A flexible, but tough finish would be best. Spar varnish is made to move with the wood, but it scratches rather easily. Epoxy finishes move enough, allow quick buildup for toughness, and scratch less. The last time I used epoxy finish, I used the system 3 epoxy finish. I think they changed the name, but it is available from Lee Valley.
It is a somewhat expensive answer, any other ideas?