How important is the horses muscles!
Well....with out them the horse can not work safely and efficiently with just their skeletal bones.
It was my own horse that lead me to find a way to increase muscle mass,tone and growth, he was extremely asymmetric on his left hind leg. As a result of not correctly engaging his core and hind legs,his muscles around the stifle were very undeveloped. This caused problems in every aspect of training a horse to carry weight on their back.
If he could not carry his own weight, How is going t carry me?