That's always what's so impressive to me.
I'm 80kg and I squat 120kg, which is not terrible, but by no means amazing.
When I see some of these people haul 600 pounds around I'm just stunned.
Imagine walking around with a 200 pounds strongman yoke, but never being able to take it off.
They do the people pretty dirty on the show usually though, by how they sort of film them from low angles and make them look even more monstrous.