I don't know about normal. Local level it isn't, but some do it to their stallions and even youngstock to make their action bigger. I have never known anyone personally who does it to be able to comment, but on the face of it it seems... not cruel but not in the animal's best interests. How can making a yearling's front feet heavy to lift and shoeing him be good for his growth and feet in later life?
Maybe an expert will come on here and prove me wrong??
I think its something that some Welsh people do, the type that keep their stallions locked up until they are ready to show them, with their bulging eyes, it encourages the horse to pick its legs up higher, but not something to be advocated.
"Proprioception is "the process by which the body can vary muscle contraction in immediate response to incoming information regarding external forces," by utilizing stretch receptors in the muscles to keep track of the joint position in the body "
Well, I am impressed!!! They obviously have a good supply of dictionaries down there