The plate drag is good.
That's a fair point about the sprints. I think I read something by Mike Boyle on the subject. There has always been a fixation on the hamstring being a flexor or an extensor when in fact they do both. Hence they get sore when you squat.
Trouble with having two arts degrees not science degrees, read a lot, don't understand or remember it all.
I gave some thought to the antagonistic relationship of the biceps and triceps recently when I notice soreness in my triceps from pullups. Didn't give it too much thought though. That could get dangerous.