The center of gravity is “C” and the effective forward or backward force is “C F. ” “P” is for paw and “C” is for center of gravity. When the paw is on the ground behind the center of gravity as in drawings 1 and 4, the paw is giving a forward push as indicated by the resultant force “C F.” When the paw is on the ground in front of the center of gravity, the resultant force is toward the rear (DECELERATING the dog) as shown in drawings 2 and 3. These results were proven in Pressure Plate* tests.

Pressure Plate tests prove that during gait cycle forward speed of the body is not uniform, even though variation is not visible to the eye.

At the gallop of any dog, the rear paw must be on the ground in front of the center of gravity (a point about in the middle of the chest) before slow down forces develop. In the gallop, approximately 90% of time a rear paw is on the ground behind the center of gravity, and is delivering a forward thrust about 90% of the time. The front paw is behind the center of gravity only about 10% of the time, and is delivering a forward thrust only 10% of that time proving the old saying that the rear delivers the drive and the front supports the dog is true.

When considering the total energy expended (work done), it takes energy to overcome either negative or positive pressure as recorded on a pressure plate. The total energy expended is in proportion to the sum (not difference) of the positive and negative forces exerted by the paw. Negative forces increase the energy expended and decrease efficiency.

DOWNWARD FORCES

The dog’s front paws carry the extra weight of the head and neck located in front of the shoulder. In theory and fact, the front paws not only carry the greater percentage of the vertical weight but also are responsible for stopping the greater percentage of the downward force due to downward momentum. Tests prove that the front absorbs nearly 3/5ths of the dog’s downward force while the rear absorbs only 2/5ths. For this reason the front foot is always larger than the rear front by about the same proportion.

* Pressure Plates were developed (early 1980s) for quantitative gait analysis. They measure the forces applied by a foot in any direction at any instant of time.

Find “Dog Locomotion and Gait Analysis” by Curtis Brown in List of Books.

The crotch of a rail fence has long been an ideal place to let the rest of the world go by or watch dogs working afield.

“Dat white ’n’ liver pup ain’t never gonna be no good,” old Henry, a Negro sage, once informed this writer from his perch on the next crotch as we watched two young derbies follow an older dog through the sedge of a field below us.

“What makes you think so?” He comes from two of the best field trial Pointers that we’ve ever cut loose.” “Mabbe he do, but look at dem withers a bobbing up ’n’ down lak Miss Irene’s rocking horse. He ain’t wuth his training.”

Henry proved to be right; the pup was a washout for endurance. The reason was that he expended most of his energy in lifting his center of gravity rather than propelling it along the line of travel. His arc was not flat enough for effective travel. He fought a battle against gravity without progress. There are several structural factors, particularly in the forequarters, which bring about this result. Fatigue will cause a marked rise and fall of an animal’s withers no matter how good might be its angulation and conformation.

“Keep your eye on a horse’s withers,” a racing trainer told us once, “and you can tell exactly when he begins to peter out. No rocking horse ever won a stake race…he’s got to keep running level to bring home the bacon.” ......

We once saw a well known Setter cut loose at a field trial streak out across the open and into the cover, working it to the far edges, then swing back into the bird-field with more time than usual for combing that. All along he seemed to be gliding rather than galloping.

The very next brace brought out a dog which at a casual glance might have been his twin, but the moment he was cut loose the resemblance ceased, for even in the open he ran as if leaping a fence at each stride. He scarcely penetrated the cover, never reached the edges, cut the course and flopped into the bird-field just as the time limit expired. He had worked much harder every minute of the time but got nowhere except up and down, wearing himself out doing it.

The major cause of the excess rise and fall of the withers is improper conformation and angulation, especially the conforming of the front and rear assemblies to one another. Two factors, thrust and lift, are involved, and they must be synchronized for efficiency. Fatigue will eventually disrupt this balance in any animal and induce a pronounced rise and fall.

Well balanced front and rear assembies allow this dog to run with an effortless gait.