I'm glad I prompted such useful info from people -- good thread.
I've been going to the gym off and on, doing all sorts of stuff including the sled thing for the legs. I can now do a set of 15 in at 300+, if I'm willing to fight for it... my knees don't seem to like it though. I've since laid off entirely, except for reps at 160, which I can do endlessly with no burn.
How does one not kill one's knees when working on the quads? I take glucosamine now... is the sled just a bad way to do it?