Well, I've gone on hikes with 70lb packs for 9 miles up and down the mountains of Camp Pendleton. I've also gone on runs wearing boots. Alot of combat exercises with packs and equipment.
When someone doesn't tie their boots properly, bad things happen. Really bad things. There was a Marine who's laces came undone, and he twisted his ankle so bad that they had to cut off the sole of his boot and then the rest of the boot off to see the damage and stop the bleeding. It was not good.