Well, this is an IPO portion of the forum. The rules call for the dog to be attentive to the handler. Period. The dog can not have eyes forward or sniffing the ground. Attentive to the handler. A dog will not hold their body in a position that hurts. It just won't happen.
Is it easy to teach heeling? No. It takes a Very long time to get the picture you want. Alot of small pieces to teach body movement, many months of luring. But you are going to get dinged for more points for the dog not being straight and the dog crowding you than you will for the head not being up. That judge falls in line behind you to watch the position.
And if your dog is not attentive to you, then you are simply not rewarding enough. It's not rocket science, it's walking with your dog beside you....not touching you, attentive to you, straight and in position.