Mechanics of locomotion of dogs (Canis familiaris) and sheep (Ovis aries)

Records have been made of the forces exerted on the ground by dogs and a sheep, in walking, trotting, cantering and slow galloping. Film has been taken simultaneously. The difference between walking and trotting was much less marked for the sheep than for the dogs. Step length and stride length increase as speed increases. They are expressed as functions of the Froude number. The vertical component of the force exerted by a foot on the ground shows two main maxima in walking, except in the case of the fore feet of sheep. In this case and in other gaits there is only one main maximum. The vertical movements of the fore and hind quarters which occurred in examples of each gait have been calculated from the force records. The force exerted by a foot on the ground changes direction in the course of a step so as to remain more or less in line with a point fixed relative to the animal, but dorsal to its back. The force records show impact disturbances in the first 003 sec of contact of each foot with the ground. The point of application of the force on the sole of a foot tends to move posteriorly as the force increases. The results are discussed in relation to a theoretical account of the mechanics of locomotion on legs.