Dogs have a great variety of shapes and sizes. Skull shape, trunk shape and limb shape and length reflect what a dog can do; their capacity to feel, their capacity to express, whether they are introverted or extroverted in giving form, and how they move.
For example a Greyhound moves predominantly with their back muscles and gives an emotional expression when they run. Great Danes predominantly use their belly or underside muscles to walk and run, feeling themselves and their surroundings as they move. Collies are beautiful and expressive in their form and Golden Retrievers are social extroverts. These qualities can be seen in their posture and their behavior, moving with their external rotators.
The differences in movement for particular breeds are a reflection of which muscle chains are anatomically more predominant parts of their structure . A Greyhound moves primarily using the back muscles on either side of the spine. Body shape and skull shape reflect which muscle chain or chains are predominant in a particular individual.
Pomeranians and Pekingese, moving primarily with intevertebral muscles, have a dancing happy gait. Problems in locomotion or frustrated or difficult behaviors can result if a dog is suppressed in their natural movement and exploration during development. This can also occur with prolonged suppression as adults. Safety to develop naturally and behave as they really are in their nature results in stability for them to be, behave and move in a manner that belongs to who they are.
The differences in movement between breeds are, in part, a reflection of which muscle chain is the natural primary or predominant muscle chain used for movement and self expression by that breed and individual.