Re: 400m time guidelines
My unscientific take:
All times for non-professional runners
I was a very average track and crosscountry runner and ran 54-56, which is better than almost anyone who doesn't train as a runner could run. It was was by no means special and I doubt I could do it anymore. I think anyone who is not a track athlete (or trains specifically for the long sprints) that can break 60 has achieved something on par with a 2x bodyweight squat. But I could be TOTALLY wrong.
I'm curious what other people think because I usually underestimate how hard I think running is and overestimate how hard I think lifting is (I CANNOT do a 2x bodyweight squat and just achieved a 2x bodyweight deadlift).