last weekend, I was carrying an 80-pound speaker and didn't see a 6-inch step down.  Instantly, my body dropped.  In my head, I had a quick flash of blown knee or lower back.  But I was fine.  I don't think a person that didn't use deadlifts & squats on a regular basis could have taken that drop.  I kept walking like it was nothing, completely shocked I didn't fall.  I had enough muscle to absorb the impact.  
it seems like most injuries (for well-trained people) occur doing silly things.
An untrained person is going to pull his back picking up groceries.  We got that shit.
But today my back got funny for a minute just bending over sideways to pick up a book off a desk I don't use.  Some weird angle of height and twisting (and it's cold/rainy).  Instant sensation of "I'm going to the ER"... then i stretched and whatever kink it was, disappeared and I was fine.