No kidding? I wonder if that is what my little Rex has. He can literally come to a stop and not move for about 5 minutes.
I have been saying for years he is a dork and lazy. I just pick him up.
Does it affect cockers or is my little guy just a little lazy?
Don't know if it's been identified in cockers or not, but what you're describing doesn't sound like it. The hind end collapses while they're still trying to run in front. Here's video showing the characteristic progress of an episode -- it's very disturbing at first glance, but then you see that the pup keeps on wagging, fetching, and looking perfectly happy even while she's dragging her hind legs. It doesn't seem to bother THEM - just their owners!
Exercise Induced Collapse
The University of Minnesota Vet School is the outfit that isolated the gene and developed the blood test.