I notice most horses working in the fields as cutters or trail animals look wide and have a big distance in their ribs, while horses in the jumping ring or racers look narrow and their ribs are shallow. I can guess that racers need a long body, so it makes them look narrow, since I don't think I have ever seen a long AND wide horse, though definitely some fat ones.
Also, is there a difference between well-sprung and wide? I think well-sprung refers to more of the curvature of the ribs outward rather than the actual distance between one side of the ribcage to the other?
Is the belly area suggestive of just the muscle, and not so much the ribcage? For example, would this horse: http://img1.findthebest.com/sites/de...orse_Ranch.jpg
Be considered more or less muscular in the belly than this horse, just judging how low the belly is: