Horses like that don't
move properly, that's why they are halter horses and not performance horses LOL. Even though many of them are not nearly so bulky when they are not fitted for shows, their conformation still leaves so much to be desired; tiny feet, chicken bones, upright pasterns, straight hocks, straight shoulders, etc, etc. Even if they do stay sound for riding, their riders usually don't because it's about like riding a jackhammer during an earthquake.
I don't want anyone to get me wrong, I've got nothing at all against the Impressive line itself (I have a grandson of his), but I don't like the way that the line is being used. It gives it such a horrible name and all of the Impressive horses I have ever dealt with have the sweetest personalities. It's a shame, really.
BTW: I do
like muscle like that on my beef cattle
. More bang for your buck LOL.