The horses eye can tell us so much about what they may be feeling. I believe so much is shown as to whether the horse is calm or stressed. Just like people, each horse has a different way of presenting their emotions and if you are paying attention to these types of details, you can learn to recognize the signs of stress, or comfort. Having education in bio mechanics, I have also learned that the horses physique goes even deeper into what a horse may be silently enduring.
What this means is that if you can educate yourself to identify correct vs. incorrect muscle development, you are saving your horse from the negative effects of muscle compensation. Everything in your body is connected, so something that impacts one part of your body affects everything else,. This can start as a minor problem, eventually turning into a major problem. Whether it is behavioral or physical signs, the first step in fixing a muscle imbalance is identifying the root cause.
When I am asked to "evaluate" a horse for either behavioral or physical issues, after requiring that a Veterinarian has ruled out any medical reasons for the changes in performance, one of the first things I will look at is the physique. This lets me know even before seeing the horse ridden what some of the underlying problems are. Wrong muscling, underdeveloped, overdeveloped, are all part of a chain reaction that interferes with the horses well being.
Muscle patterns are definitely a window to the horses soul.