I did a thread on linear progression with HST, BTW. It works better for me, keeping me closer to failure and limiting zigzag effect. Won't work for everybody tho.
Myths. That could take all night. If you have a few (more than a few: $45) bucks, you'll have a ball with "Knowledge and Nonsense" by Coach Jamie Hale.
Much is said about the pitfalls of failure training in here, but many of us grew on it. Before our joints and CNS couldn't take any more...
Shock training...good for a minnit; don't make a habit.
Oh, let's see, there's muscle "confusion", constant tension, things like supervolume (which I'm not entirely sure doesn't work in some cases) and many silly exersizes that waste gym time.
I like to say that we need a change AFTER we've adapted ourselves onto a plateau and consistently lose progress. Guys who change constantly are missing the concept of training. They usually don't get very strong either, IMO.
Oh, why are you so focused on PR's? They're not the endall and beall of this sport, nor is your growth dependent upon them. Sometimes we get TOO goal-oriented and lose the enjoyment. That can be debilitating. Old age (such as it is) has me enjoying the heck out of beating the clock, staying disciplined, being generally strong, and of course there is that occasional workout that totally just ROCKS...keeps you fired up until the next one. But I get that without PR's - it's beating the iron and being the master of my day.
Bedtime: Peace/out.